C語言設計前中後隊列實例代碼

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隊列基本概念

隊列是最常見的概念，日常生活經常需要排隊，仔細觀察隊列會發現，隊列是一種邏輯結構，是一種特殊的線性表。特殊在：

隻能在固定的兩端操作線性表

隻要滿足上述條件，那麼這種特殊的線性表就會呈現出一種“先進先出”的邏輯，這種邏輯就被稱為隊列。

由於約定瞭隻能在線性表固定的兩端進行操作，於是給隊列這種特殊的線性表的插入刪除，起個特殊的名稱：

隊頭：可以刪除節點的一端

隊尾：可以插入節點的一端

入隊：將節點插入到隊尾之後，函數名通常為enQueue()

出隊：將隊頭節點從隊列中剔除，函數名通常為outQueue()

取隊頭：取得隊頭元素，但不出隊，函數名通常為front()

本題就是手擼數據結構中基本的隊列結構，常用的有兩種，一種是用鏈表實現，一種是數組實現。本文將會給出兩種實現方式

1，數組實現

typedef struct {
    int value[1000];
    int len;
} FrontMiddleBackQueue;
 
 
FrontMiddleBackQueue* frontMiddleBackQueueCreate() {
    FrontMiddleBackQueue *queue = (FrontMiddleBackQueue *)malloc(sizeof(FrontMiddleBackQueue));
    memset(queue,0,sizeof(FrontMiddleBackQueue));
    return queue;
}
 
void insert(FrontMiddleBackQueue* obj, int pos, int val)
{
    //在pos位置插入val，則pos(從0開始)位置後的數統一向後挪一個位置,隊列長度加1
    int i = 0;
    for(i=obj->len; i>pos; i--)
    {
        obj->value[i] = obj->value[i-1];
    }
    obj->value[pos] = val;
    obj->len++;
}
 
int pop(FrontMiddleBackQueue* obj, int pos)
{
    //彈出pos位置的val,則pos(從0開始)位置後向前統一挪一個位置，隊列長度減一
    if(obj->len == 0)
        return -1;
    int i = 0;
    int popval = obj->value[pos]; //先將pos位置的數保存下來，不然下面的移位操作就覆蓋瞭pos位置的值
    for(i=pos; i<obj->len-1; i++)
    {
        obj->value[i] = obj->value[i+1];
    }
    obj->len--;
    return popval;
}
 
void frontMiddleBackQueuePushFront(FrontMiddleBackQueue* obj, int val) {
    insert(obj,0,val);
}
 
void frontMiddleBackQueuePushMiddle(FrontMiddleBackQueue* obj, int val) {
    insert(obj,obj->len/2,val);
}
 
void frontMiddleBackQueuePushBack(FrontMiddleBackQueue* obj, int val) {
    insert(obj,obj->len,val);
}
 
int frontMiddleBackQueuePopFront(FrontMiddleBackQueue* obj) {
    return pop(obj,0);
}
 
int frontMiddleBackQueuePopMiddle(FrontMiddleBackQueue* obj) {
    return pop(obj,(obj->len-1)/2);
}
 
int frontMiddleBackQueuePopBack(FrontMiddleBackQueue* obj) {
    return pop(obj, obj->len-1);
}
 
void frontMiddleBackQueueFree(FrontMiddleBackQueue* obj) {
    free(obj);
}
 
/**
 * Your FrontMiddleBackQueue struct will be instantiated and called as such:
 * FrontMiddleBackQueue* obj = frontMiddleBackQueueCreate();
 * frontMiddleBackQueuePushFront(obj, val);
 
 * frontMiddleBackQueuePushMiddle(obj, val);
 
 * frontMiddleBackQueuePushBack(obj, val);
 
 * int param_4 = frontMiddleBackQueuePopFront(obj);
 
 * int param_5 = frontMiddleBackQueuePopMiddle(obj);
 
 * int param_6 = frontMiddleBackQueuePopBack(obj);
 
 * frontMiddleBackQueueFree(obj);
*/

運行結果

 2，鏈表實現

1，設計鏈表結構，鏈表維持一個頭節點和尾結點，頭節點始終在最前面並且頭結點的data存儲整個隊列的節點數，尾結點始終是最後一個節點

2，設計插入節點函數和刪除節點函數，push和pop操作隻需要根據不同場景傳入不同的參數即可完成統一的操作

typedef struct tag_Node {
    int data;
    struct tag_Node* next, *prev;
}Node;
 
 
typedef struct {
    Node* front;
    Node* rear;
} FrontMiddleBackQueue;
 
 
FrontMiddleBackQueue* frontMiddleBackQueueCreate() {
    FrontMiddleBackQueue* que = (FrontMiddleBackQueue *)malloc(sizeof(FrontMiddleBackQueue));
    que->front = (Node *)malloc(sizeof(Node));
    que->rear = (Node *)malloc(sizeof(Node));
    que->front->data = 0;
    que->front->next = NULL;
    que->rear->data = 0;
    que->rear->next = NULL;
    que->front->next = que->rear;
    que->rear->prev = que->front;
    
    return que;
}
 
void AddNode(FrontMiddleBackQueue* obj, Node *cur, int val) 
{
    Node* addNode = (Node *)malloc(sizeof(Node));
    addNode->data = val;
    addNode->prev = cur->prev;
    addNode->next = cur;
    
    cur->prev->next = addNode;
    cur->prev = addNode;
    
    obj->front->data++;
    return;
}
 
Node* GetMiddleNode(FrontMiddleBackQueue* obj, bool isAdd)
{
    Node* tmp = obj->front->next;
    
    int len = isAdd ? (obj->front->data / 2) : ((obj->front->data - 1) / 2);
    for (int i = 0; i < len; i++) {
        tmp = tmp->next;
    }
    return tmp;
}
 
void frontMiddleBackQueuePushFront(FrontMiddleBackQueue* obj, int val) {
    AddNode(obj, obj->front->next, val);
    return;
}
 
void frontMiddleBackQueuePushMiddle(FrontMiddleBackQueue* obj, int val) {
    AddNode(obj, GetMiddleNode(obj, true), val);
    return;
}
 
void frontMiddleBackQueuePushBack(FrontMiddleBackQueue* obj, int val) {
    AddNode(obj, obj->rear, val);
    return;
}
 
int RemoveNode(FrontMiddleBackQueue* obj, Node* cur)
{
    if (obj->front->data == 0) {
        return -1;
    }
    cur->next->prev = cur->prev;
    cur->prev->next = cur->next;
 
    obj->front->data--;
    int item = cur->data;
    free(cur);
    return item;
}
 
int frontMiddleBackQueuePopFront(FrontMiddleBackQueue* obj) {
    return RemoveNode(obj, obj->front->next);
}
 
int frontMiddleBackQueuePopMiddle(FrontMiddleBackQueue* obj) {
    return RemoveNode(obj, GetMiddleNode(obj, false));
}
 
int frontMiddleBackQueuePopBack(FrontMiddleBackQueue* obj) {
    return RemoveNode(obj, obj->rear->prev);
}
 
void frontMiddleBackQueueFree(FrontMiddleBackQueue* obj) {
    while (RemoveNode(obj, obj->front->next) != -1);
    free(obj->front);
    free(obj->rear);
    free(obj);
    return;
}
 
/**
 * Your FrontMiddleBackQueue struct will be instantiated and called as such:
 * FrontMiddleBackQueue* obj = frontMiddleBackQueueCreate();
 * frontMiddleBackQueuePushFront(obj, val);
 
 * frontMiddleBackQueuePushMiddle(obj, val);
 
 * frontMiddleBackQueuePushBack(obj, val);
 
 * int param_4 = frontMiddleBackQueuePopFront(obj);
 
 * int param_5 = frontMiddleBackQueuePopMiddle(obj);
 
 * int param_6 = frontMiddleBackQueuePopBack(obj);
 
 * frontMiddleBackQueueFree(obj);
*/

運行結果：

 總結

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