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std:: erase_if (std::unordered_multiset)

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C++
Containers library
std::unordered_multiset
Member types
Member functions
Non-member functions
erase_if (std::unordered_multiset)
(C++20)
Deduction guides (C++17)
定义于头文件 <unordered_set>
template < class Key, class Hash, class KeyEqual, class Alloc,

class Pred >
std:: unordered_multiset < Key, Hash, KeyEqual, Alloc > :: size_type
erase_if ( std:: unordered_multiset < Key, Hash, KeyEqual, Alloc > & c,

Pred pred ) ;
(C++20 起)
(C++26 起为 constexpr)

从 c 中擦除所有满足谓词 pred 的元素。

等同于 

auto old_size = c.size();
for (auto first = c.begin(), last = c.end(); first != last;)
{
    if (pred(*first))
        first = c.erase(first);
    else
        ++first;
}
return old_size - c.size();

目录

参数

c - 要从中擦除元素的容器
pred - 谓词，当元素应被擦除时返回 true

返回值

被擦除的元素数量。

复杂度

线性。

示例

运行此代码 
#include <iostream>
#include <unordered_set>
void println(auto rem, const auto& container)
{
    std::cout << rem << '{';
    for (char sep[]{0, ' ', 0}; const auto& item : container)
        std::cout << sep << item, *sep = ',';
    std::cout << "}\n";
}
int main()
{
    std::unordered_multiset data{3, 3, 4, 5, 5, 6, 6, 7, 2, 1, 0};
    println("Original:\n", data);
    auto divisible_by_3 = [](const auto& x) { return (x % 3) == 0; };
    const auto count = std::erase_if(data, divisible_by_3);
    println("Erase all items divisible by 3:\n", data);
    std::cout << count << " items erased.\n";
}

可能的输出： 

Original:
{0, 1, 2, 7, 6, 6, 5, 5, 4, 3, 3}
Erase all items divisible by 3:
{1, 2, 7, 5, 5, 4}
5 items erased.

参见

移除满足特定条件的元素
(函数模板)
(C++20) (C++20)
移除满足特定条件的元素
(算法函数对象)