C++ STL中的map :: clear()

Map是像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()函数用于从地图容器中删除所有元素，从而使其大小保持为0。

句法：

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

Parameters:
No parameters are passed.

返回值：无

例子：

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

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

// CPP program to illustrate
// Implementation of clear() function
#include 
using namespace std;
  
int main()
{
    // Take any two maps
    map 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)

要从最佳影片策划和实践问题去学习，检查了C++基础课程为基础，以先进的C++和C++ STL课程基础加上STL。要完成从学习语言到DS Algo等的更多准备工作，请参阅“完整面试准备课程” 。