C++控制臺實現簡單註冊登錄

#include<iostream>
#include<string>
#include <vector>
#include <conio.h>
void Display();//調用display顯示switch()界面
void Register();//註冊
void Enter();//登錄
using namespace std; 
 class user{
 private:
 string ID;
 string Name;
 string Email;
 string Password;
 public:
 user(){};
 void Register();
 void Enter();
 } ;
 vector<user> people;
 
 void user:: Register()//註冊
 {
 string pw1;
 string pw2;
 user person;
 cout<<"請設置您的ID：";
 flag:
 cin>>person.ID;
 for(int i=0;i<people.size();i++){
 if(people.at(i).ID==person.ID){
 cout<<"該ID已存在，請重新設置:";
 goto flag;
 }
 }
 cout<<"請設置您的用戶名：";
 cin>>person.Name;
 cout<<"請綁定您的郵箱：";
 cin>>person.Email;
 cout<<"請設置您的密碼：";
 flag0:
 cin>>pw1;
 cout<<"請再次確認您的密碼：";
 cin>>pw2;
 if(pw1!=pw2)
 {
 cout<<"前後兩次輸入密碼不一致，請重新設置密碼:";
 goto flag0;
 }
 cout<<"註冊成功！"<<endl;
 person.Password=pw1;
 people.push_back(person);
 Display();
 }
 void user::Enter()//登錄
 {
 cout<<"請輸入您的ID：";
 flag1:
 string id;
 string pwd;
 cin>>id;
 for(int i=0;i<people.size();i++){//驗證ID是否存在
 int tk=1;tk++;
 if(people.at(i).ID==id){
 tk=2;
 cout<<"請輸入您的密碼：";
 flag2:
 cin>>pwd;
 if(people.at(i).Password!=pwd){
 cout<<"密碼錯誤，請重新輸入:";
 goto flag2;
 }
 cout<<"登錄成功！"<<endl;
 cout<<" (1)Information查看信息\n (2)Exit退出\n\nChoice:";
 int choice;//選擇界面
 cin>>choice; switch(choice)
 {
 case 1://查看信息
 cout<<"您的ID為："<<people.at(i).ID<<endl;
 cout<<"您的密碼為："<<people.at(i).Password<<endl;
 cout<<"您的用戶名為："<<people.at(i).Name<<endl;
 cout<<"您的郵箱為："<<people.at(i).Email<<endl;
 Display();
 case 2://退出
  exit(EXIT_FAILURE);
 }
 }
 }
 cout<<"該ID不存在，請重新輸入:";
 goto flag1;
 }
 
 void Display()//界面
 {
 cout<<" (1)Register註冊\n (2)Enter登錄\n (3)Exit退出\n\nChoice:";
 int choice;//選擇界面
 user u;
 cin>>choice; switch(choice)
 {
 case 1://註冊
  u.Register();//調用函數
  break;
 case 2://登錄
  u.Enter();//調用函數
  break;
 case 3://退出
 exit(EXIT_FAILURE);
 }
 }
 int main()
 {
 Display();//顯示界面　　１註冊；２登錄；3退出
 cin.get();
 return 0;
}