C++頭文件algorithm中的函數功能詳解

C++中的算法都是通過函數模板實現,所以STL的數據結構,甚至是自己定義的數據結構基本都可以調用內置算法。掌握C++內置算法,可以幫助我們節省大量的時間!

1. 不修改內容的序列操作

(1)all_of

查找是否所有元素滿足條件。

在range[first,last)中,所有pred都為真,或者range范圍為空,返回true,否則返回false。

template <class InputIterator, class UnaryPredicate>
  bool all_of (InputIterator first, InputIterator last, UnaryPredicate pred);

舉例:

#include <iostream>     // std::cout
#include <algorithm>    // std::all_of
#include<list>

int main () {
  //std::array<int,8> foo = {3,5,7,11,13,17,19,23};
  std::list<int> foo = {3,5,7,11,13,17,19,23};

  if ( std::all_of(foo.begin(), foo.end(), [](int i){return i%2;}) )
    std::cout << "All the elements are odd numbers.\n";//奇數

  return 0;
}

(2)any_of

查找是否有元素滿足條件。

在range[first,last)中,pred至少有一個為真,或者range范圍為空,返回true,否則返回false。用法同all_of。

template <class InputIterator, class UnaryPredicate>
  bool any_of (InputIterator first, InputIterator last, UnaryPredicate pred);

(3)none_of

查找是否所有元素都不滿足條件。

在range[first,last)中,pred沒有一個為真,或者range范圍為空,返回true,否則返回false。用法同all_of。

template <class InputIterator, class UnaryPredicate>
  bool none_of (InputIterator first, InputIterator last, UnaryPredicate pred);

(4)for_each

對range [first,last)中的每一個元素,都執行fn函數操作。

  • fn可以是普通函數也可以是仿函數(函數對象)。
  • fn後面不可以添加括號
template <class InputIterator, class Function>
   Function for_each (InputIterator first, InputIterator last, Function fn);

代碼舉例:

#include <iostream>     // std::cout
#include <algorithm>    // std::for_each
#include <vector>       // std::vector

void myfunction (int i) {  // function:普通函數
  std::cout << ' ' << i;
}

struct myclass {           // function object type:,仿函數,或者函數對象
  void operator() (int i) {std::cout << ' ' << i;}
} myobject;

int main () {
  std::vector<int> myvector;
  myvector.push_back(10);
  myvector.push_back(20);
  myvector.push_back(30);

  std::cout << "myvector contains:";
  for_each (myvector.begin(), myvector.end(), myfunction);
  std::cout << '\n';

  // or:
  std::cout << "myvector contains:";
  for_each (myvector.begin(), myvector.end(), myobject);
  std::cout << '\n';

  return 0;
}

(5)find

查找第一個和所提供變量相同的元素。

從 range [first,last)依次尋找元素,如果找到第一個與val相同相同的元素,則返回它的迭代器,否則返回last的迭代器。

template <class InputIterator, class T>
   InputIterator find (InputIterator first, InputIterator last, const T& val);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::find
#include <vector>       // std::vector

int main () {
  // using std::find with array and pointer:
  int myints[] = { 10, 20, 30, 40 };
  int * p;

  p = std::find (myints, myints+4, 30);
  if (p != myints+4)
    std::cout << "Element found in myints: " << *p << '\n';
  else
    std::cout << "Element not found in myints\n";

  // using std::find with vector and iterator:
  std::vector<int> myvector (myints,myints+4);
  std::vector<int>::iterator it;

  it = find (myvector.begin(), myvector.end(), 30);
  if (it != myvector.end())
    std::cout << "Element found in myvector: " << *it << '\n';
  else
    std::cout << "Element not found in myvector\n";

  return 0;
}

輸出:

Element found in myints: 30
Element found in myvector: 30

(6)find_if

查找第一個滿足條件的元素。

從 range [first,last)依次尋找元素,如果找到第一個使得pred為真的元素,則返回它的迭代器,否則返回last迭代器。

template <class InputIterator, class UnaryPredicate>
   InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred);

代碼舉例:

尋找第一個奇數

#include <iostream>     // std::cout
#include <algorithm>    // std::find_if
#include <vector>       // std::vector

bool IsOdd (int i) {
  return ((i%2)==1);
}

int main () {
  std::vector<int> myvector;

  myvector.push_back(10);
  myvector.push_back(25);
  myvector.push_back(40);
  myvector.push_back(55);

  std::vector<int>::iterator it = std::find_if (myvector.begin(), myvector.end(), IsOdd);
  std::cout << "The first odd value is " << *it << '\n';//奇數

  return 0;
}

輸出:

The first odd value is 25

(7)find_if_not

查找第一個不滿足條件的元素。

從 range [first,last)依次尋找元素,如果找到第一個使得pred為假的元素,則返回它的迭代器,否則返回last迭代器。

template <class InputIterator, class UnaryPredicate>
   InputIterator find_if_not (InputIterator first, InputIterator last, UnaryPredicate pred);

代碼舉例:

尋找第一個偶數

#include <iostream>     // std::cout
#include <algorithm>    // std::find_if_not
#include <array>        // std::array

int main () {
  std::array<int,5> foo = {1,2,3,4,5};

  std::array<int,5>::iterator it =
    std::find_if_not (foo.begin(), foo.end(), [](int i){return i%2;} );
  std::cout << "The first even value is " << *it << '\n';

  return 0;
}

輸出:

The first even value is 2

(8)find_end

模板1:查找最後一個相同的序列。

在range [first1,last1) 去尋找[first2,last2)的元素,如果找到最後一個(不是第一個)被匹配的元素,則范圍第一個被匹配的迭代器,否則范圍last1的迭代器。

模板2:查找最後一個滿足條件的序列。

在range [first1,last1) 去尋找[first2,last2)的元素,如果找到最後一個(不是第一個)滿足pred條件的元素,則范圍第一個被匹配的迭代器,否則范圍last1的迭代器。

//equality (1)	
template <class ForwardIterator1, class ForwardIterator2>
   ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,
                              ForwardIterator2 first2, ForwardIterator2 last2);
//predicate (2)	
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
   ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,
                              ForwardIterator2 first2, ForwardIterator2 last2,
                              BinaryPredicate pred);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::find_end
#include <vector>       // std::vector

bool myfunction (int i, int j) {
  return (i==j);
}

int main () {
  int myints[] = {1,2,3,4,5,1,2,3,4,5};
  std::vector<int> haystack (myints,myints+10);

  int needle1[] = {1,2,3};

  // using default comparison:
  std::vector<int>::iterator it;
  it = std::find_end (haystack.begin(), haystack.end(), needle1, needle1+3);

  if (it!=haystack.end())
    std::cout << "needle1 last found at position " << (it-haystack.begin()) << '\n';

  int needle2[] = {4,5,1};

  // using predicate comparison:
  it = std::find_end (haystack.begin(), haystack.end(), needle2, needle2+3, myfunction);

  if (it!=haystack.end())
    std::cout << "needle2 last found at position " << (it-haystack.begin()) << '\n';

  return 0;
}

輸出:

needle1 last found at position 5
needle2 last found at position 3

(9)find_first_of

和find_end類似,隻不過它是尋找第一個匹配的元素。

//equality (1)	
template <class InputIterator, class ForwardIterator>
   InputIterator find_first_of (InputIterator first1, InputIterator last1,
                                   ForwardIterator first2, ForwardIterator last2);
//predicate (2)	
template <class InputIterator, class ForwardIterator, class BinaryPredicate>
   InputIterator find_first_of (InputIterator first1, InputIterator last1,
                                   ForwardIterator first2, ForwardIterator last2,
                                   BinaryPredicate pred);

(10)adjacent_find

模板1:從范圍 range [first,last)中尋找連續相同元素。

模板2:找到滿足條件pred的迭代器。

如果找到,則范圍范圍內的第一個滿足的迭代器,否則范圍last的迭代器。

//equality (1)	
template <class ForwardIterator>
   ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last);
//predicate (2)	
template <class ForwardIterator, class BinaryPredicate>
   ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last,
                                  BinaryPredicate pred);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::adjacent_find
#include <vector>       // std::vector

bool myfunction (int i, int j) {
  return (i==j);
}

int main () {
  int myints[] = {5,20,5,30,30,20,10,10,20};
  std::vector<int> myvector (myints,myints+8);
  std::vector<int>::iterator it;

  // using default comparison:
  it = std::adjacent_find (myvector.begin(), myvector.end());

  if (it!=myvector.end())
    std::cout << "the first pair of repeated elements are: " << *it << '\n';

  //using predicate comparison:
  it = std::adjacent_find (++it, myvector.end(), myfunction);//從上一個已經找到的地方開始

  if (it!=myvector.end())
    std::cout << "the second pair of repeated elements are: " << *it << '\n';

  return 0;
}

輸出:

the first pair of repeated elements are: 30
the second pair of repeated elements are: 10

(11)count

在range [first,last)中,計算與val相同的元素個數。

template <class InputIterator, class T>
  typename iterator_traits<InputIterator>::difference_type
    count (InputIterator first, InputIterator last, const T& val);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::count
#include <vector>       // std::vector

int main () {
  // counting elements in array:
  int myints[] = {10,20,30,30,20,10,10,20};   // 8 elements
  int mycount = std::count (myints, myints+8, 10);
  std::cout << "10 appears " << mycount << " times.\n";

  // counting elements in container:
  std::vector<int> myvector (myints, myints+8);
  mycount = std::count (myvector.begin(), myvector.end(), 20);
  std::cout << "20 appears " << mycount  << " times.\n";

  return 0;
}

輸出:

10 appears 3 times.
20 appears 3 times.

(12)count_if

在range [first,last)中,計算讓pred為真的元素個數。

template <class InputIterator, class UnaryPredicate>
  typename iterator_traits<InputIterator>::difference_type
    count_if (InputIterator first, InputIterator last, UnaryPredicate pred);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::count_if
#include <vector>       // std::vector

bool IsOdd (int i) { return ((i%2)==1); }

int main () {
  std::vector<int> myvector;
  for (int i=1; i<10; i++) myvector.push_back(i); // myvector: 1 2 3 4 5 6 7 8 9

  int mycount = count_if (myvector.begin(), myvector.end(), IsOdd);
  std::cout << "myvector contains " << mycount  << " odd values.\n";

  return 0;
}

輸出:

myvector contains 5 odd values.

(13)mismatch

找出兩個序列不匹配的開始點,或者找出兩個序列不滿足條件pred的開始點。

模板1:first2與range [first1,last1) 范圍內的元素對比,返回第一個都不匹配的迭代器組pair(first1, first2)。

模板2:first2與range [first1,last1) 范圍內的元素對比,返回第一個不滿足條件pred的迭代器組pair(first1, first2)。

//equality (1)	
template <class InputIterator1, class InputIterator2>
  pair<InputIterator1, InputIterator2>
    mismatch (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2);
//predicate (2)	
template <class InputIterator1, class InputIterator2, class BinaryPredicate>
  pair<InputIterator1, InputIterator2>
    mismatch (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2, BinaryPredicate pred);

代碼舉例:

#include <iostream>     // std::cout
#include <algorithm>    // std::mismatch
#include <vector>       // std::vector
#include <utility>      // std::pair

bool mypredicate (int i, int j) {
  return (i==j);
}

int main () {
  std::vector<int> myvector;
  for (int i=1; i<6; i++) myvector.push_back (i*10); // myvector: 10 20 30 40 50

  int myints[] = {10,20,80,320,1024};                //   myints: 10 20 80 320 1024

  std::pair<std::vector<int>::iterator,int*> mypair;

  // using default comparison:
  mypair = std::mismatch (myvector.begin(), myvector.end(), myints);
  std::cout << "First mismatching elements: " << *mypair.first;
  std::cout << " and " << *mypair.second << '\n';

  ++mypair.first; ++mypair.second;

  // using predicate comparison:
  mypair = std::mismatch (mypair.first, myvector.end(), mypair.second, mypredicate);
  std::cout << "Second mismatching elements: " << *mypair.first;
  std::cout << " and " << *mypair.second << '\n';

  return 0;
}

輸出:

First mismatching elements: 30 and 80
Second mismatching elements: 40 and 320

(14)equal

判斷兩個序列是否相等,或者滿足條件pred。

如果兩個序列都相等,或者都滿足條件pred,則返回true。

//equality (1)	
template <class InputIterator1, class InputIterator2>
  bool equal (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2);
//predicate (2)	
template <class InputIterator1, class InputIterator2, class BinaryPredicate>
  bool equal (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2, BinaryPredicate pred);

代碼舉例:

#include <iostream>     // std::cout
#include <algorithm>    // std::equal
#include <vector>       // std::vector

bool mypredicate (int i, int j) {
  return (i==j);
}

int main () {
  int myints[] = {20,40,60,80,100};               //   myints: 20 40 60 80 100
  std::vector<int>myvector (myints,myints+5);     // myvector: 20 40 60 80 100

  // using default comparison:
  if ( std::equal (myvector.begin(), myvector.end(), myints) )
    std::cout << "The contents of both sequences are equal.\n";
  else
    std::cout << "The contents of both sequences differ.\n";

  myvector[3]=81;                                 // myvector: 20 40 60 81 100

  // using predicate comparison:
  if ( std::equal (myvector.begin(), myvector.end(), myints, mypredicate) )
    std::cout << "The contents of both sequences are equal.\n";
  else
    std::cout << "The contents of both sequences differ.\n";

  return 0;
}

輸出:

The contents of both sequences are equal.
The contents of both sequences differ.

(15)is_permutation

permutation的意思是排列,組合的意思。也就是判斷兩個序列是不是隻是重新組合瞭。

//equality (1)	
template <class ForwardIterator1, class ForwardIterator2>
   bool is_permutation (ForwardIterator1 first1, ForwardIterator1 last1,
                        ForwardIterator2 first2);
//predicate (2)	
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
   bool is_permutation (ForwardIterator1 first1, ForwardIterator1 last1,
                        ForwardIterator2 first2, BinaryPredicate pred);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::is_permutation
#include <array>        // std::array

int main () {
  std::array<int,5> foo = {1,2,3,4,5};
  std::array<int,5> bar = {3,1,4,5,2};

  if ( std::is_permutation (foo.begin(), foo.end(), bar.begin()) )
    std::cout << "foo and bar contain the same elements.\n";

  return 0;
}

輸出:

foo and bar contain the same elements.

(16)search

在 range [first1,last1)中尋找[first2,last2)子序列,找到則返回第一個相等或滿足條件的迭代器,否則范圍last1迭代器。

//equality (1)	
template <class ForwardIterator1, class ForwardIterator2>
   ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2);
//predicate (2)	
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
   ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2,
                            BinaryPredicate pred);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::search
#include <vector>       // std::vector

bool mypredicate (int i, int j) {
  return (i==j);
}

int main () {
  std::vector<int> haystack;

  // set some values:        haystack: 10 20 30 40 50 60 70 80 90
  for (int i=1; i<10; i++) haystack.push_back(i*10);

  // using default comparison:
  int needle1[] = {40,50,60,70};
  std::vector<int>::iterator it;
  it = std::search (haystack.begin(), haystack.end(), needle1, needle1+4);

  if (it!=haystack.end())
    std::cout << "needle1 found at position " << (it-haystack.begin()) << '\n';
  else
    std::cout << "needle1 not found\n";

  // using predicate comparison:
  int needle2[] = {20,30,50};
  it = std::search (haystack.begin(), haystack.end(), needle2, needle2+3, mypredicate);

  if (it!=haystack.end())
    std::cout << "needle2 found at position " << (it-haystack.begin()) << '\n';
  else
    std::cout << "needle2 not found\n";

  return 0;
}

輸出:

needle1 found at position 3
needle2 not found

(17)search_n

在 range [first,last)序列中,找出和val相等的個數,或者滿足條件的pred的個數,找到則返回第一個滿足條件的迭代器(指向最後一個滿足計數的迭代器),否則返回last迭代器。

//equality (1)	
template <class ForwardIterator, class Size, class T>
   ForwardIterator search_n (ForwardIterator first, ForwardIterator last,
                             Size count, const T& val);
//predicate (2)	
template <class ForwardIterator, class Size, class T, class BinaryPredicate>
   ForwardIterator search_n ( ForwardIterator first, ForwardIterator last,
                              Size count, const T& val, BinaryPredicate pred );

2. 修改內容的序列操作

(1)copy

復制range [first,last)的元素到result迭代器開始的序列中。result的范圍不應該和[first,last)重疊。

template <class InputIterator, class OutputIterator>
  OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result);

代碼舉例:

#include <iostream>     // std::cout
#include <algorithm>    // std::copy
#include <vector>       // std::vector

int main () {
  int myints[]={10,20,30,40,50,60,70};
  std::vector<int> myvector (7);

  std::copy ( myints, myints+7, myvector.begin() );

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it = myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;

  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 10 20 30 40 50 60 70

(2)copy_n

復制從first開始的n個元素,到result中。

template <class InputIterator, class Size, class OutputIterator>
  OutputIterator copy_n (InputIterator first, Size n, OutputIterator result);

(3)copy_if

復制range [first,last)中滿足條件pred的元素,到result中。

template <class InputIterator, class OutputIterator, class UnaryPredicate>
  OutputIterator copy_if (InputIterator first, InputIterator last,
                          OutputIterator result, UnaryPredicate pred);

(4)copy_backward

和copy類似,隻不過copy_backward是從後面開始復制。

和copy一樣,不允許重疊。

template <class BidirectionalIterator1, class BidirectionalIterator2>
  BidirectionalIterator2 copy_backward (BidirectionalIterator1 first,
                                        BidirectionalIterator1 last,
                                        BidirectionalIterator2 result);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::copy_backward
#include <vector>       // std::vector

int main () {
  std::vector<int> myvector;

  // set some values:
  for (int i=1; i<=5; i++)
    myvector.push_back(i*10);          // myvector: 10 20 30 40 50

  myvector.resize(myvector.size()+3);  // allocate space for 3 more elements

  std::copy_backward ( myvector.begin(), myvector.begin()+5, myvector.end() );

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 10 20 30 10 20 30 40 50

(5)move

從[first,last)的元素移動到result中,原來的元素狀態是有效的,但是元素的值不確定。

move移動時候,不應該有重疊。

template <class InputIterator, class OutputIterator>
  OutputIterator move (InputIterator first, InputIterator last, OutputIterator result);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::move (ranges)
#include <utility>      // std::move (objects)
#include <vector>       // std::vector
#include <string>       // std::string

int main () {
  std::vector<std::string> foo = {"air","water","fire","earth"};
  std::vector<std::string> bar (4);

  // moving ranges:
  std::cout << "Moving ranges...\n";
  std::move ( foo.begin(), foo.begin()+4, bar.begin() );

  std::cout << "foo contains " << foo.size() << " elements:";
  std::cout << " (each in an unspecified but valid state)";
  std::cout << '\n';

  std::cout << "bar contains " << bar.size() << " elements:";
  for (std::string& x: bar) std::cout << " [" << x << "]";
  std::cout << '\n';

  // moving container:
  std::cout << "Moving container...\n";
  foo = std::move (bar);

  std::cout << "foo contains " << foo.size() << " elements:";
  for (std::string& x: foo) std::cout << " [" << x << "]";
  std::cout << '\n';

  std::cout << "bar is in an unspecified but valid state";
  std::cout << '\n';

  return 0;
}

輸出:

Moving ranges…
foo contains 4 elements: (each in an unspecified but valid state)
bar contains 4 elements: [air] [water] [fire] [earth]
Moving container…
foo contains 4 elements: [air] [water] [fire] [earth]
bar is in an unspecified but valid state

(6)move_backward

從range [first,last)中移動數據到result中,不過result是末尾。類似於copy_backward。

move_backward移動的時候,不應該有重疊。下面的示例沒有重疊。

template <class BidirectionalIterator1, class BidirectionalIterator2>
  BidirectionalIterator2 move_backward (BidirectionalIterator1 first,
                                        BidirectionalIterator1 last,
                                        BidirectionalIterator2 result);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::move_backward
#include <string>       // std::string

int main () {
  std::string elems[10] = {"air","water","fire","earth"};

  // insert new element at the beginning:
  std::move_backward (elems,elems+4,elems+5);
  elems[0]="ether";

  std::cout << "elems contains:";
  for (int i=0; i<10; ++i)
    std::cout << " [" << elems[i] << "]";
  std::cout << '\n';

  return 0;
}

輸出:

elems contains: [ether] [air] [water] [fire] [earth] [] [] [] [] []

(7)swap

C++11已經把該函數移到<utility>頭文件中,已經不在<algorithm>中。

模板1:不修改地址,隻交換值。

模板2:交換序列值的內容和大小。

交換兩個元素的值,相應地址也會交換

//non-array (1)	
template <class T> void swap (T& a, T& b)
  noexcept (is_nothrow_move_constructible<T>::value && is_nothrow_move_assignable<T>::value);
//array (2)	
template <class T, size_t N> void swap(T (&a)[N], T (&b)[N])
  noexcept (noexcept(swap(*a,*b)));

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::swap
#include <vector>       // std::vector

int main () {
  int x=10, y=20;                              // x:10 y:20
   std::cout<<"x add: "<<&x << "y add: "<< &y<<std::endl;
  std::swap(x,y);                              // x:20 y:10
  std::cout<<"x add: "<<&x << "y add: "<< &y<<std::endl;

  //x:20 ,y: 10
  std::vector<int> foo (4,x), bar (6,y);       // foo:4x20 bar:6x10
  std::swap(foo,bar);                          // foo:6x10 bar:4x20

  std::cout << "foo contains:";
  for (std::vector<int>::iterator it=foo.begin(); it!=foo.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  std::cout << "bar contains:";
  for (std::vector<int>::iterator it=bar.begin(); it!=bar.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

x add: 0x7ffc1528b7e8y add: 0x7ffc1528b7ec
x add: 0x7ffc1528b7e8y add: 0x7ffc1528b7ec
foo contains: 10 10 10 10 10 10
bar contains: 20 20 20 20

(8)swap_ranges

隻交換一部分數據,從range [first1,last1) 對應位置,交換first2開始的值。

template <class ForwardIterator1, class ForwardIterator2>
  ForwardIterator2 swap_ranges (ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::swap_ranges
#include <vector>       // std::vector

int main () {
  std::vector<int> foo (5,10);        // foo: 10 10 10 10 10
  std::vector<int> bar (5,33);        // bar: 33 33 33 33 33

  std::swap_ranges(foo.begin()+1, foo.end()-1, bar.begin());

  // print out results of swap:
  std::cout << "foo contains:";
  for (std::vector<int>::iterator it=foo.begin(); it!=foo.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  std::cout << "bar contains:";
  for (std::vector<int>::iterator it=bar.begin(); it!=bar.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

foo contains: 10 33 33 33 10
bar contains: 10 10 10 33 33

(9)iter_swap

隻交換兩個序列中,兩個迭代器所指向的一個值。

template <class ForwardIterator1, class ForwardIterator2>
  void iter_swap (ForwardIterator1 a, ForwardIterator2 b);

代碼示例:

int main () {

  int myints[]={10,20,30,40,50 };              //   myints:  10  20  30  40  50
  std::vector<int> myvector (4,99);            // myvector:  99  99  99  99

  std::iter_swap(myints,myvector.begin());     //   myints: [99] 20  30  40  50
                                                                                        // myvector: [10] 99  99  99

  std::iter_swap(myints+3,myvector.begin()+2); //   myints:  99  20  30 [99] 50
                                                                                                // myvector:  10  99 [40] 99

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(10)transform

模板1:對 range [first1,last1)都執行op操作,然後復制給result。range [first1,last1)中的元素不會改變。

模板2:range [first1,last1)中的每個元素都和first2開始的元素,依次執行binary_op操作,然後復制給result。

//unary operation(1)	
template <class InputIterator, class OutputIterator, class UnaryOperation>
  OutputIterator transform (InputIterator first1, InputIterator last1,
                            OutputIterator result, UnaryOperation op);
//binary operation(2)	
template <class InputIterator1, class InputIterator2,
          class OutputIterator, class BinaryOperation>
  OutputIterator transform (InputIterator1 first1, InputIterator1 last1,
                            InputIterator2 first2, OutputIterator result,
                            BinaryOperation binary_op);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::transform
#include <vector>       // std::vector
#include <functional>   // std::plus

int op_increase (int i) { return ++i; }

int main () {
  std::vector<int> foo;
  std::vector<int> bar;

  // set some values:
  for (int i=1; i<6; i++)
    foo.push_back (i*10);                         // foo: 10 20 30 40 50

  bar.resize(foo.size());                         // allocate space

  std::transform (foo.begin(), foo.end(), bar.begin(), op_increase);
                                                  // bar: 11 21 31 41 51

  // std::plus adds together its two arguments:
  std::transform (foo.begin(), foo.end(), bar.begin(), foo.begin(), std::plus<int>());
                                                  // foo: 21 41 61 81 101

  std::cout << "foo contains:";
  for (std::vector<int>::iterator it=foo.begin(); it!=foo.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(11)replace

對 range [first,last) 中所有的old_value元素,使用new_value替換。

template <class ForwardIterator, class T>
  void replace (ForwardIterator first, ForwardIterator last,
                const T& old_value, const T& new_value);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::replace
#include <vector>       // std::vector

int main () {
  int myints[] = { 10, 20, 30, 30, 20, 10, 10, 20 };
  std::vector<int> myvector (myints, myints+8);            // 10 20 30 30 20 10 10 20

  std::replace (myvector.begin(), myvector.end(), 20, 99); // 10 99 30 30 99 10 10 99

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 10 99 30 30 99 10 10 99

(12)replace_if

替換所有使得pred為真的元素。

template <class ForwardIterator, class UnaryPredicate, class T>
  void replace_if (ForwardIterator first, ForwardIterator last,
                   UnaryPredicate pred, const T& new_value );

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::replace_if
#include <vector>       // std::vector

bool IsOdd (int i) { return ((i%2)==1); }

int main () {
  std::vector<int> myvector;

  // set some values:
  for (int i=1; i<10; i++) myvector.push_back(i);               // 1 2 3 4 5 6 7 8 9

  std::replace_if (myvector.begin(), myvector.end(), IsOdd, 0); // 0 2 0 4 0 6 0 8 0

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(13)replace_copy

從range [first,last) 拷貝元素到以result為起始的迭代器中, 並修改old_value為new_value。原來的序列元素保持不變。

template <class InputIterator, class OutputIterator, class T>
  OutputIterator replace_copy (InputIterator first, InputIterator last,
                               OutputIterator result,
                               const T& old_value, const T& new_value);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::replace_copy
#include <vector>       // std::vector

int main () {
  int myints[] = { 10, 20, 30, 30, 20, 10, 10, 20 };

  std::vector<int> myvector (8);
  std::replace_copy (myints, myints+8, myvector.begin(), 20, 99);

  for(auto x:myints)
      std::cout<<x<<", ";
  std::cout<<std::endl;

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

10, 20, 30, 30, 20, 10, 10, 20,
myvector contains: 10 99 30 30 99 10 10 99

(14)replace_copy_if

從range [first,last) 拷貝元素到以result為起始的迭代器中, 如果滿足pred為真,元素修改為new_value。原來的序列元素保持不變。

template <class InputIterator, class OutputIterator, class UnaryPredicate, class T>
  OutputIterator replace_copy_if (InputIterator first, InputIterator last,
                                  OutputIterator result, UnaryPredicate pred,
                                  const T& new_value);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::replace_copy_if
#include <vector>       // std::vector

bool IsOdd (int i) { return ((i%2)==1); }

int main () {
  std::vector<int> foo,bar;

  // set some values:
  for (int i=1; i<10; i++) foo.push_back(i);          // 1 2 3 4 5 6 7 8 9

  bar.resize(foo.size());   // allocate space
  std::replace_copy_if (foo.begin(), foo.end(), bar.begin(), IsOdd, 0);
                                                        // 0 2 0 4 0 6 0 8 0,隻修改奇數

  std::cout << "bar contains:";
  for (std::vector<int>::iterator it=bar.begin(); it!=bar.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(15)fill

使用val填充 range [first,last)。

template <class ForwardIterator, class T>
  void fill (ForwardIterator first, ForwardIterator last, const T& val);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::fill
#include <vector>       // std::vector

int main () {
  std::vector<int> myvector (8);                       // myvector: 0 0 0 0 0 0 0 0

  std::fill (myvector.begin(),myvector.begin()+4,5);   // myvector: 5 5 5 5 0 0 0 0
  std::fill (myvector.begin()+3,myvector.end()-2,8);   // myvector: 5 5 5 8 8 8 0 0

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 5 5 5 8 8 8 0 0

(16)fill_n

填充n個val元素到以first開始的序列

template <class OutputIterator, class Size, class T>
  OutputIterator fill_n (OutputIterator first, Size n, const T& val);

(17)generate

以gen規則生成的元素,依次復制給 range [first,last)。

template <class ForwardIterator, class Generator>
  void generate (ForwardIterator first, ForwardIterator last, Generator gen);

(18)generate_n

以gen規則生成的元素,依次復制給以first開始的n個元素。

template <class OutputIterator, class Size, class Generator>
  OutputIterator generate_n (OutputIterator first, Size n, Generator gen);

(19)remove

刪除 range [first,last)中和val相同的元素,並返回新序列的end迭代器。

template <class ForwardIterator, class T>
  ForwardIterator remove (ForwardIterator first, ForwardIterator last, const T& val);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::remove

int main () {
  int myints[] = {10,20,30,30,20,10,10,20};      // 10 20 30 30 20 10 10 20

  // bounds of range:
  int* pbegin = myints;                          // ^
  int* pend = myints+sizeof(myints)/sizeof(int); // ^                       ^

  pend = std::remove (pbegin, pend, 20);         // 10 30 30 10 10 ?  ?  ?
                                                 // ^              ^
  std::cout << "range contains:";
  for (int* p=pbegin; p!=pend; ++p)
    std::cout << ' ' << *p;
  std::cout << '\n';

  return 0;
}

輸出:

range contains: 10 30 30 10 10

(20)remove_if

刪除 range [first,last)中滿足pred條件的元素,並返回新序列的end迭代器。

template <class ForwardIterator, class UnaryPredicate>
  ForwardIterator remove_if (ForwardIterator first, ForwardIterator last,
                             UnaryPredicate pred);

(21)remove_copy

除瞭和val相同的元素,復制range [first,last)中的元素到result開始的元素中。原來的序列保持不變。

template <class InputIterator, class OutputIterator, class T>
  OutputIterator remove_copy (InputIterator first, InputIterator last,
                              OutputIterator result, const T& val);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::remove_copy
#include <vector>       // std::vector

int main () {
  int myints[] = {10,20,30,30,20,10,10,20};               // 10 20 30 30 20 10 10 20
  std::vector<int> myvector (8);

  std::remove_copy (myints,myints+8,myvector.begin(),20); // 10 30 30 10 10 0 0 0

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(22)remove_copy_if

除瞭使得pred為真的元素,復制range [first,last)中的元素到result開始的元素中。原來的序列保持不變。

template <class InputIterator, class OutputIterator, class UnaryPredicate>
  OutputIterator remove_copy_if (InputIterator first, InputIterator last,
                                 OutputIterator result, UnaryPredicate pred);

(23)unique

在range[first,last)中,如果遇到連續的相同元素,隻保留第一個。並返回處理完畢之後的end迭代器。

刪除的地方補0,可以用resize去掉。

模板1:默認相等

模板2:自定義pred相等規則

//equality (1)	
template <class ForwardIterator>
  ForwardIterator unique (ForwardIterator first, ForwardIterator last);
//predicate (2)	
template <class ForwardIterator, class BinaryPredicate>
  ForwardIterator unique (ForwardIterator first, ForwardIterator last,
                          BinaryPredicate pred);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::unique, std::distance
#include <vector>       // std::vector

bool myfunction (int i, int j) {
  return (i==j);
}

int main () {
  int myints[] = {10,20,20,20,30,30,20,20,10};           // 10 20 20 20 30 30 20 20 10
  std::vector<int> myvector (myints,myints+9);

  // using default comparison:
  std::vector<int>::iterator it;
  it = std::unique (myvector.begin(), myvector.end());   // 10 20 30 20 10 ?  ?  ?  ?,指向第一個?

  myvector.resize( std::distance(myvector.begin(),it) ); // 10 20 30 20 10

  // using predicate comparison:
  std::unique (myvector.begin(), myvector.end(), myfunction);   // (no changes)

  // print out content:
  std::cout << "myvector contains:";
  for (it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 10 20 30 20 10

(24)unique_copy

復制unique元素到result中,原來的元素保持不變。

//equality (1)	
template <class InputIterator, class OutputIterator>
  OutputIterator unique_copy (InputIterator first, InputIterator last,
                              OutputIterator result);
//predicate (2)	
template <class InputIterator, class OutputIterator, class BinaryPredicate>
  OutputIterator unique_copy (InputIterator first, InputIterator last,
                              OutputIterator result, BinaryPredicate pred);

(25)reverse

反轉序列

template <class BidirectionalIterator>
  void reverse (BidirectionalIterator first, BidirectionalIterator last);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::reverse
#include <vector>       // std::vector

int main () {
  std::vector<int> myvector;

  // set some values:
  for (int i=1; i<10; ++i) myvector.push_back(i);   // 1 2 3 4 5 6 7 8 9

  std::reverse(myvector.begin(),myvector.end());    // 9 8 7 6 5 4 3 2 1

  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(26)reverse_copy

復制反轉的序列,原來的序列保持不變

template <class BidirectionalIterator, class OutputIterator>
  OutputIterator reverse_copy (BidirectionalIterator first,
                               BidirectionalIterator last, OutputIterator result);

(27)rotate

以middle為圓點,調換左右序列,其中middle迭代器指向的元素為第一個元素。。

template <class ForwardIterator>
  ForwardIterator rotate (ForwardIterator first, ForwardIterator middle,
                          ForwardIterator last);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::rotate
#include <vector>       // std::vector

int main () {
  std::vector<int> myvector;

  // set some values:
  for (int i=1; i<10; ++i) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9

  std::rotate(myvector.begin(),myvector.begin()+3,myvector.end());
                                                  // 4 5 6 7 8 9 1 2 3
  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 4 5 6 7 8 9 1 2 3

(28)rotate_copy

復制旋轉過的元素到result中,但是原來的序列保持不變。這一點像reverse_copy。

template <class ForwardIterator, class OutputIterator>
  OutputIterator rotate_copy (ForwardIterator first, ForwardIterator middle,
                              ForwardIterator last, OutputIterator result);

(29)random_shuffle

shuffle意思是洗牌。

gen是自己定義的隨機種子。

//generator by default (1)	
template <class RandomAccessIterator>
  void random_shuffle (RandomAccessIterator first, RandomAccessIterator last);
//specific generator (2)	
template <class RandomAccessIterator, class RandomNumberGenerator>
  void random_shuffle (RandomAccessIterator first, RandomAccessIterator last,
                       RandomNumberGenerator&& gen);

(30)shuffle

也是重新洗牌。

template <class RandomAccessIterator, class URNG>
  void shuffle (RandomAccessIterator first, RandomAccessIterator last, URNG&& g);

3. 劃分操作(Partitions)

(1)is_partitioned

(2)partition

(3)stable_partition

(4)partition_copy

(5)partition_point

4. 排序操作(sorting)

(1)sort

默認排序:升序
模板2:根據comp返回true的狀態排序

不保證相同元素,保持原來的排序方法。如果需要保持原來的順序,可以使用stable_sort。

//default (1)	
template <class RandomAccessIterator>
  void sort (RandomAccessIterator first, RandomAccessIterator last);
//custom (2)	
template <class RandomAccessIterator, class Compare>
  void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::sort
#include <vector>       // std::vector

bool myfunction (int i,int j) { return (i<j); }

struct myclass {
  bool operator() (int i,int j) { return (i<j);}
} myobject;

int main () {
  int myints[] = {32,71,12,45,26,80,53,33};
  std::vector<int> myvector (myints, myints+8);               // 32 71 12 45 26 80 53 33

  // using default comparison (operator <):
  std::sort (myvector.begin(), myvector.begin()+4);           //(12 32 45 71)26 80 53 33

  // using function as comp
  std::sort (myvector.begin()+4, myvector.end(), myfunction); // 12 32 45 71(26 33 53 80)普通函數

  // using object as comp
  std::sort (myvector.begin(), myvector.end(), myobject);     //(12 26 32 33 45 53 71 80)函數對象

  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

(2)stable_sort

和sort一樣,隻不過相同元素保持原來的排序。

(3)partial_sort

middle之前的元素,都是小於或等於middle,而且經過排序。middle之後的元素沒有指定順序。

//default (1)	
template <class RandomAccessIterator>
  void partial_sort (RandomAccessIterator first, RandomAccessIterator middle,
                     RandomAccessIterator last);
//custom (2)	
template <class RandomAccessIterator, class Compare>
  void partial_sort (RandomAccessIterator first, RandomAccessIterator middle,
                     RandomAccessIterator last, Compare comp);

(4)partial_sort_copy

從range [first,last),復制最小的一部分元素,到 [result_first,result_last),並排序。原來的序列保持不變。

[first,last)小於[result_first,result_last)則隻截取最小的一部分,否則全部排序並復制。

模板1:默認升排序

模板2:自定義comp規則。

//default (1)	
template <class InputIterator, class RandomAccessIterator>
  RandomAccessIterator
    partial_sort_copy (InputIterator first,InputIterator last,
                       RandomAccessIterator result_first,
                       RandomAccessIterator result_last);
//custom (2)	
template <class InputIterator, class RandomAccessIterator, class Compare>
  RandomAccessIterator
    partial_sort_copy (InputIterator first,InputIterator last,
                       RandomAccessIterator result_first,
                       RandomAccessIterator result_last, Compare comp);

(5)is_sorted

判斷序列是否排序。

模板1:默認排序

模板2:自定義comp規則。

//default (1)	
template <class ForwardIterator>
  bool is_sorted (ForwardIterator first, ForwardIterator last);
//custom (2)	
template <class ForwardIterator, class Compare>
  bool is_sorted (ForwardIterator first, ForwardIterator last, Compare comp);

(6)is_sorted_until

模板1:返回第一個不滿足默認升排序的迭代器

模板2:返回第一個不滿足自定義comp規則的迭代器。

//default (1)	
template <class ForwardIterator>
  ForwardIterator is_sorted_until (ForwardIterator first, ForwardIterator last);
//custom (2)	
template <class ForwardIterator, class Compare>
  ForwardIterator is_sorted_until (ForwardIterator first, ForwardIterator last,
                                   Compare comp);

(7)nth_element

重新排列range [first,last)元素。nth左邊的元素是小的,右邊的元素是大的。

模板1:默認排序。

模板2:comp規則

//default (1)	
template <class RandomAccessIterator>
  void nth_element (RandomAccessIterator first, RandomAccessIterator nth,
                    RandomAccessIterator last);
//custom (2)	
template <class RandomAccessIterator, class Compare>
  void nth_element (RandomAccessIterator first, RandomAccessIterator nth,
                    RandomAccessIterator last, Compare comp);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::nth_element, std::random_shuffle
#include <vector>       // std::vector

bool myfunction (int i,int j) { return (i<j); }

int main () {
  std::vector<int> myvector;

  // set some values:`在這裡插入代碼片`
  for (int i=1; i<10; i++) myvector.push_back(i);   // 1 2 3 4 5 6 7 8 9

  std::random_shuffle (myvector.begin(), myvector.end());//洗牌

  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  // using default comparison (operator <):
  //以myvector.begin()+5為中心
  std::nth_element (myvector.begin(), myvector.begin()+5, myvector.end());

  // using function as comp
  std::nth_element (myvector.begin(), myvector.begin()+5, myvector.end(),myfunction);

  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

輸出:

myvector contains: 5 4 8 9 1 6 3 2 7
myvector contains: 5 2 3 1 4 6 7 8 9

5. 二分查找操作(Binary search)

二分查找需要所有元素經過排序。

(1)lower_bound

模板1:返回第一個不小於val元素指向的迭代器。

模板2:依據comp規則,返回第一個不小於val的元素的迭代器。

模板1內所有元素都是通過”<“排序,模板2都是通過comp排序。

//default (1)	
template <class ForwardIterator, class T>
  ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last,
                               const T& val);
//custom (2)	
template <class ForwardIterator, class T, class Compare>
  ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last,
                               const T& val, Compare comp);
#include <iostream>     // std::cout
#include <algorithm>    // std::lower_bound, std::upper_bound, std::sort
#include <vector>       // std::vector

int main () {
  int myints[] = {10,20,30,30,20,10,10,20};
  std::vector<int> v(myints,myints+8);           // 10 20 30 30 20 10 10 20

  std::sort (v.begin(), v.end());                // 10 10 10 20 20 20 30 30

  std::vector<int>::iterator low,up;
  low=std::lower_bound (v.begin(), v.end(), 20); // 指向第一個20
  up= std::upper_bound (v.begin(), v.end(), 20); // 指向20後面第一個大於20的元素

  std::cout << "lower_bound at position " << (low- v.begin()) << '\n';
  std::cout << "upper_bound at position " << (up - v.begin()) << '\n';

  return 0;
}

輸出:

lower_bound at position 3
upper_bound at position 6

(2)upper_bound

模板1:返回第一個大於val元素指向的迭代器

模板2:依據comp規則,返回第一個大於val的元素的迭代器。

模板1內所有元素都是通過”<“排序,模板2都是通過comp排序。

//default (1)	
template <class ForwardIterator, class T>
  ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last,
                               const T& val);
//custom (2)	
template <class ForwardIterator, class T, class Compare>
  ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last,
                               const T& val, Compare comp);

(3)equal_range

模板1:返回 range [first,last)內,所有等於val元素的邊界對pair(low, upper)。

模板2:返回 range [first,last)內,所有等於val元素的邊界對pair(low, upper)。

模板1內所有元素都是通過”<“排序,模板2都是通過comp排序。

//default (1)	
template <class ForwardIterator, class T>
  pair<ForwardIterator,ForwardIterator>
    equal_range (ForwardIterator first, ForwardIterator last, const T& val);
//custom (2)	
template <class ForwardIterator, class T, class Compare>
  pair<ForwardIterator,ForwardIterator>
    equal_range (ForwardIterator first, ForwardIterator last, const T& val,
                  Compare comp);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::equal_range, std::sort
#include <vector>       // std::vector

bool mygreater (int i,int j) { return (i>j); }

int main () {
  int myints[] = {10,20,30,30,20,10,10,20};
  std::vector<int> v(myints,myints+8);                         // 10 20 30 30 20 10 10 20
  std::pair<std::vector<int>::iterator,std::vector<int>::iterator> bounds;

  // using default comparison:
  std::sort (v.begin(), v.end());                                  // 10 10 10 20 20 20 30 30
  bounds=std::equal_range (v.begin(), v.end(), 20);//          ^                ^

  // using "mygreater" as comp:
  std::sort (v.begin(), v.end(), mygreater);                                       // 30 30 20 20 20 10 10 10
  bounds=std::equal_range (v.begin(), v.end(), 20, mygreater); //       ^                 ^

  std::cout << "bounds at positions " << (bounds.first - v.begin());
  std::cout << " and " << (bounds.second - v.begin()) << '\n';

  return 0;
}

輸出:

bounds at positions 2 and 5

(4)binary_search

range [first,last)中的元素至少有一個等於val,則返回true,否則返回false。

序列應該按照默認升序或者comp規則排序。

//default (1)	
template <class ForwardIterator, class T>
  bool binary_search (ForwardIterator first, ForwardIterator last,
                      const T& val);
//custom (2)	
template <class ForwardIterator, class T, class Compare>
  bool binary_search (ForwardIterator first, ForwardIterator last,
                      const T& val, Compare comp);

6. 集合(Merge)

(1)merge

(2)inplace_merge

(3)includes

(4)set_union

(5)set_intersection

(6)set_difference

(7)set_symmetric_difference

 7. 堆操作

(1)push_heap

(2)pop_heap

(3)make_heap

(4)sort_heap

(5)is_heap

(6)is_heap_until

8. 最小最大值操作

(1)min

返回兩個元素的最小的一個。

模板1:內置數據類型

模板2和模板3:自己定義comp

模板3可以有多個元素。

//default (1)	
template <class T> constexpr const T& min (const T& a, const T& b);
//custom (2)	
template <class T, class Compare>
  constexpr const T& min (const T& a, const T& b, Compare comp);
//initializer list (3)	
template <class T> constexpr T min (initializer_list<T> il);
template <class T, class Compare>
  constexpr T min (initializer_list<T> il, Compare comp);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::min

int main () {
  std::cout << "min(1,2)==" << std::min(1,2) << '\n';
  std::cout << "min(2,1)==" << std::min(2,1) << '\n';
  std::cout << "min('a','z')==" << std::min('a','z') << '\n';
  std::cout << "min(3.14,2.72)==" << std::min(3.14,2.72) << '\n';


 std::cout<<std::min({1,2,4,5,6,7})<<std::endl;
  return 0;
}

輸出:

min(1,2)==1
min(2,1)==1
min(‘a’,’z’)==a
min(3.14,2.72)==2.72
1

(2)max

同min

(3)minmax

返回make_pair(a,b),a為最小值,b為最大值。

模板3可以有多個元素。

//default (1)	
template <class T>
  constexpr pair <const T&,const T&> minmax (const T& a, const T& b);
//custom (2)	
template <class T, class Compare>
  constexpr pair <const T&,const T&> minmax (const T& a, const T& b, Compare comp);
//initializer list (3)	
template <class T>
  constexpr pair<T,T> minmax (initializer_list<T> il);
template <class T, class Compare>
  constexpr pair<T,T> minmax (initializer_list<T> il, Compare comp);

(4)min_element

模板1:返回最小元素的迭代器

模板2:根據comp的小於號定義規則(一定要升序),不然結果相反。

//default (1)	
template <class ForwardIterator>
  ForwardIterator min_element (ForwardIterator first, ForwardIterator last);
//custom (2)	
template <class ForwardIterator, class Compare>
  ForwardIterator min_element (ForwardIterator first, ForwardIterator last,
                               Compare comp);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::min_element, std::max_element

bool myfn(int i, int j) { return i<j; }

struct myclass {
  bool operator() (int i,int j) { return i<j; }
} myobj;

int main () {
  int myints[] = {3,7,2,5,6,4,9};

  // using default comparison:
  std::cout << "The smallest element is " << *std::min_element(myints,myints+7) << '\n';
  std::cout << "The largest element is "  << *std::max_element(myints,myints+7) << '\n';

  // using function myfn as comp:
  std::cout << "The smallest element is " << *std::min_element(myints,myints+7,myfn) << '\n';
  std::cout << "The largest element is "  << *std::max_element(myints,myints+7,myfn) << '\n';

  // using object myobj as comp:
  std::cout << "The smallest element is " << *std::min_element(myints,myints+7,myobj) << '\n';
  std::cout << "The largest element is "  << *std::max_element(myints,myints+7,myobj) << '\n';

  return 0;
}

輸出:

The smallest element is 2
The largest element is 9
The smallest element is 2
The largest element is 9
The smallest element is 2
The largest element is 9

(5)max_element

同min_element

(6)minmax_element

同minmax規則,不過返回的是迭代器。

9. 其他

(1)lexicographical_compare

類似於字符串比較大小,這裡可以自定義數據類型比較。[first1,last1) 的元素小於[first2,last2),則返回true。

模板1:默認小於

模板2:自定義comp判斷。

//default (1)	
template <class InputIterator1, class InputIterator2>
  bool lexicographical_compare (InputIterator1 first1, InputIterator1 last1,
                                InputIterator2 first2, InputIterator2 last2);
//custom (2)	
template <class InputIterator1, class InputIterator2, class Compare>
  bool lexicographical_compare (InputIterator1 first1, InputIterator1 last1,
                                InputIterator2 first2, InputIterator2 last2,
                                Compare comp);

代碼示例:

#include <iostream>     // std::cout, std::boolalpha
#include <algorithm>    // std::lexicographical_compare
#include <cctype>       // std::tolower

// a case-insensitive comparison function:
bool mycomp (char c1, char c2)
{ return std::tolower(c1)<std::tolower(c2); }//自定義,轉換成小寫比較

int main () {
  char foo[]="Apple";
  char bar[]="apartment";

  std::cout << std::boolalpha;

  std::cout << "Comparing foo and bar lexicographically (foo<bar):\n";

  std::cout << "Using default comparison (operator<): ";
  std::cout << std::lexicographical_compare(foo,foo+5,bar,bar+9);
  std::cout << '\n';

  std::cout << "Using mycomp as comparison object: ";
  std::cout << std::lexicographical_compare(foo,foo+5,bar,bar+9,mycomp);
  std::cout << '\n';

  return 0;
}

輸出:

Comparing foo and bar lexicographically (foo<bar):
Using default comparison (operator<): true
Using mycomp as comparison object: false

(2)next_permutation

  • permutation表示排序。
  • 獲取比現在的數據排列大的一組數據,並獲取新的排列。比如比1,2,3大的下一次排列為1,3,2.
  • 如果已經是最大排序,那麼它先獲取下一次的排序,比如321下一次的排序為123,並返回false。

模板1:默認排序

模板2:自定義comp排序

//default (1)	
template <class BidirectionalIterator>
  bool next_permutation (BidirectionalIterator first,
                         BidirectionalIterator last);
//custom (2)	
template <class BidirectionalIterator, class Compare>
  bool next_permutation (BidirectionalIterator first,
                         BidirectionalIterator last, Compare comp);

代碼示例:

#include <iostream>     // std::cout
#include <algorithm>    // std::next_permutation, std::sort

int main () {
  int myints[] = {1,2,3};

  std::sort (myints,myints+3);

  std::cout << "The 3! possible permutations with 3 elements:\n";
  do {
    std::cout << myints[0] << ' ' << myints[1] << ' ' << myints[2] << '\n';
  } while ( std::next_permutation(myints,myints+3) );

  std::cout << "After loop: " << myints[0] << ' ' << myints[1] << ' ' << myints[2] << '\n';

  return 0;
}

輸出結果:

The 3! possible permutations with 3 elements:
1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1
After loop: 1 2 3

(3)prev_permutation

用法同next_permutation,隻不過它獲取的是下一次的較大值。


參考:http://www.cplusplus.com/reference/algorithm/

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