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2. C ++标准库
3. unordered_map::erase

unordered_map::erase

描述 (Description)

C ++函数std::unordered_map::erase()删除与密钥k关联的映射值。

声明 (Declaration)

以下是std :: unordered_map :: erase（）函数形式std :: unordered_map头的声明。

C++11

size_type erase(const key_type& k);

参数 (Parameters)

k - 要删除的元素的键。

返回值

返回删除的元素数。

时间复杂

常数即O（1）

例子 (Example)

以下示例显示了std :: unordered_map :: erase（）函数的用法。

#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;
}

让我们编译并运行上面的程序，这将产生以下结果 -

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