C++ map::clear()用法及代码示例

Map是字典一样的数据结构。它是(键，值)对的关联数组，其中每个唯一键仅与单个值相关联。

map::clear()
clear()函数用于从Map容器中删除所有元素，从而使其大小保持为0。

用法:

map1.clear()
where map1 is the name of the map.

参数：
No parameters are passed.

返回值：没有

例子：

Input:map1 = { 
                {1, "India"},
                {2, "Nepal"},
                {3, "Sri Lanka"},
                {4, "Myanmar"}
               }
        map1.clear();
Output:map1 = {}

Input:map2 = {}
        map2.clear();
Output:map2 = {}

推荐：请尝试一下{IDE}首先，在继续解决方案之前。

// CPP program to illustrate 
// Implementation of clear() function 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // Take any two maps 
    map<int, string> map1, map2; 
      
    // Inserting values 
    map1[1] = "India"; 
    map1[2] = "Nepal"; 
    map1[3] = "Sri Lanka"; 
    map1[4] = "Myanmar"; 
      
    // Print the size of map 
    cout<< "Map size before running function:\n"; 
    cout << "map1 size = " << map1.size() << endl; 
    cout << "map2 size = " << map2.size() << endl;; 
      
    // Deleting the map elements 
    map1.clear(); 
    map2.clear(); 
      
    // Print the size of map 
    cout<< "Map size after running function:\n"; 
    cout << "map1 size = " << map1.size() << endl; 
    cout << "map2 size = " << map2.size(); 
    return 0; 
}

输出：

Map size before running function:
map1 size = 4
map2 size = 0
Map size after running function:
map1 size = 0
map2 size = 0

时间复杂度：线性即O(n)

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注：本文由纯净天空筛选整理自AKASH GUPTA 6大神的英文原创作品 map::clear() in C++ STL。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。