C++ unordered_map empty用法及代码示例

// CPP program to illustrate 
// Implementation of unordered_map empty() function 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // Take any two unordered_map 
    unordered_map<int, int> ump1, ump2; 
  
    // Inserting values 
    ump1[1] = 2; 
    ump1[3] = 4; 
    ump1[5] = 6; 
    ump1[7] = 8; 
  
    // Print the size of container 
    cout << "ump1 size = " << ump1.size() << endl; 
    cout << "ump2 size = " << ump2.size() << endl; 
  
    // Running the function for ump1 
    if (ump1.empty()) 
        cout << "True\n"; 
    else
        cout << "False\n"; 
  
    // Running the function for ump2 
    if (ump2.empty()) 
        cout << "True\n"; 
    else
        cout << "False\n"; 
  
    // Running the function for ump1 after 
    // clearing it 
    ump1.clear(); 
    if (ump1.empty()) 
        cout << "True\n"; 
    else
        cout << "False\n"; 
  
    return 0; 
}