C++ Unordered_map erase()用法及代碼示例

描述

C++ 函數std::unordered_map::erase()刪除與鍵關聯的映射值k。

聲明

以下是 std::unordered_map::erase() 函數形式 std::unordered_map 頭文件的聲明。

C++11

size_type erase(const key_type& k);

參數

k─ 要刪除的元素的鍵。

返回值

返回移除的元素數。

時間複雜度

常數，即 O(1)

示例

下麵的例子展示了 std::unordered_map::erase() 函數的用法。

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_map<char, int> um = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5}
            };

   cout << "Unordered map contains following elements before erase operation" << endl;

   for (auto it = um.begin(); it != um.end(); ++it)
      cout << it->first << " = " << it->second << endl;

   um.erase('a');

   cout << endl;
   cout << "Unordered map contains following elements after erase operation" << endl;

   for (auto it = um.begin(); it != um.end(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

讓我們編譯並運行上麵的程序，這將產生以下結果——

Unordered map contains following elements before erase operation
e = 5
a = 1
b = 2
c = 3
d = 4
Unordered map contains following elements after erase operation
e = 5
b = 2
c = 3
d = 4