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C++ Multimap 中的 operator>=函数

C++ operator>= 是C++中multimap的非成员重载函数。此函数用于检查第一个multimap是否大于或等于其他。

Note: Operator >= 顺序比较multimap的元素，比较将在第一次不匹配时停止。

operator>= - 语法

template <class Key, class T, class Compare, class Alloc>  
  bool operator>=  ( const multimap<Key,T,Compare,Alloc>& lhs,  
                    const multimap<Key,T,Compare,Alloc>& rhs );

operator>= - 参数

lhs :第一个multimap对象。

rhs :第二个multimap对象。

operator>= - 返回值

如果multimap集合对象的左侧大于或等于multimap集合对象的右侧，则返回 true ，否则返回 false 。

operator>= - 例子1

让我们看一个简单的示例，检查第一个multimap是否大于或等于:

在线运行复制代码

#include <iostream>  
#include <map>  
  
using namespace std;  
  
int main() {  
   multimap<char, int> m1;  
   multimap<char, int> m2;  
  
   m1.emplace('a', 1);  
   m2.emplace('a', 1);  
  
   if (m1 >= m2)  
      cout << "Multimap m1 is greater than or equal to m2." << endl;  
  
   m2.emplace('b', 2);  
  
   if (!(m1 >= m2))  
      cout << "Multimap m1 is not greater than or equal to m2." << endl;  
  
   return 0;  
}

输出:

Multimap m1 is greater than or equal to m2.
Multimap m1 is not greater than or equal to m2.

在上面的示例中，有两个multimapm1和m2。 m1和m2包含一个元素。当我们比较两个multimap时，它将显示消息"multimapm1大于或等于m2"，并且在向m2添加一个元素之后，它将显示消息"multimapm1不大于或等于m2"。

operator>= - 例子2

让我们看一个简单的例子:

在线运行复制代码

#include <map>    
#include <iostream>    
    
using namespace std;   
     
int main( )    
{     
   multimap < int, int > m1, m2, m3, m4;    
   int i;    
   typedef pair < int, int > Int_Pair;    
    
   for ( i = 1 ; i < 3 ; i++ )    
   {    
      m1.insert ( Int_Pair ( i, i ) );    
      m2.insert ( Int_Pair ( i, i * i ) );    
      m3.insert ( Int_Pair ( i, i - 1 ) );    
      m4.insert ( Int_Pair ( i, i ) );    
   }    
    
   if ( m1 >= m2 )    
      cout << "Multimap m1 is greater than or equal to multimap m2." << endl;    
   else    
      cout << "The multimap m1 is less than the multimap m2." << endl;    
    
   if ( m1 >= m3 )    
      cout << "Multimap m1 is greater than or equal to multimap m3." << endl;    
   else    
      cout << "The multimap m1 is less than the multimap m3." << endl;    
    
   if ( m1 >= m4 )    
      cout << "Multimap m1 is greater than or equal to multimap m4." << endl;    
   else    
      cout << "The multimap m1 is less than the multimap m4." << endl;    
        
      return 0;  
}

输出:

The multimap m1 is less than the multimap m2.
Multimap m1 is greater than or equal to multimap m3.
Multimap m1 is greater than or equal to multimap m4.

operator>= - 例子3

让我们看一个简单的例子:

在线运行复制代码

#include <iostream>  
#include <map>  
  
using namespace std;  
  
int main()  
{  
  multimap<char,int> m1, m2;  
  m1.insert(make_pair('a',10));  
  m1.insert(make_pair('b',20));  
  m1.insert(make_pair('a',30));  
  m2 = m1;  
  
  cout << (m1 >= m2) << endl;  
  
  m2.insert(make_pair('d',40));  
  
  cout << (m1 >= m2) << endl;  
  
  return 0;  
}

输出:

1
0

在上面的示例中，如果m1大于或等于m2，则它将返回1，否则返回0。

operator>= - 例子4

复制代码

#include <map>    
#include <iostream>    
using namespace std;   
    
int main ()    
{    
   multimap<int,string> m2;  
   typedef multimap<int,string> login;   
     
   m2.insert({2040, "xyz@123"}) ; //stored id and password  
     
   string password;  
   int id;  
   login m1;  
     
       cout<<"---------Login----------"<<endl<<endl;  
       cout<<"Enter the ID and password: \n";  
       cin>> id;             //Get key  
       cin>> password;      //Get value  
       m1.insert({id, password});  //Put them in multimap  
  
     cout<<"ID and password you have entered: \n";  
     for (auto it = m1.begin(); it != m1.end(); it++) {  
        cout << (*it).first << "    " << (*it).second << endl;  
      }  
      cout<<"ID and Password stored in the system :\n";  
     for (auto it = m2.begin(); it != m2.end(); it++) {  
        cout << (*it).first << "    " << (*it).second << endl;  
     }  
  
    
   if (m1 >= m2)    
        cout << "\nWelcome to your Page..." << endl;  
   else    
        cout << "\nIncorrect ID or Password..." << endl;  
      return 0;  
}

输出:

1).
---------Login----------

Enter the ID and password: 
1020     xyz
ID and password you have entered: 
1020     xyz
ID and Password stored in the system:
2040     xyz@123

Incorrect ID or Password...


2).
---------Login----------

Enter the ID and password: 
2040     xyz@123
ID and password you have entered: 
2040     xyz@123
ID and Password stored in the system:
2040     xyz@123

Welcome to your Page...

在上面的示例中，有两个multimapm1和m2。 m1包含存储的ID和密码，第二个multimapm2存储用户输入的ID和密码。它检查m1是否大于或等于m2。如果m1的ID和密码大于或等于m2，则登录成功，否则登录失败。

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