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std:: erase, std:: erase_if (std::inplace_vector)

From cppreference.net

C++
Containers library
std::inplace_vector
Member types
Member functions
Non-member functions
erase (std::inplace_vector) erase_if (std::inplace_vector)
定义于头文件 <inplace_vector>
template < class T, std:: size_t N, class U = T >

constexpr typename std:: inplace_vector < T, N > :: size_type

erase ( std:: inplace_vector < T, N > & c, const U & value ) ;
(1) (C++26 起)
template < class T, std:: size_t N, class Pred >

constexpr typename std:: inplace_vector < T, N > :: size_type

erase_if ( std:: inplace_vector < T, N > & c, Pred pred ) ;
(2) (C++26 起)
1) 从容器的 c 中擦除所有与 value 比较相等的元素。等价于 auto it = std :: remove ( c. begin ( ) , c. end ( ) , value ) ;
auto r = std:: distance ( it, c. end ( ) ) ;
c. erase ( it, c. end ( ) ) ;
return r ; 。
2) 从容器的 c 中擦除所有满足谓词 pred 的元素。等价于 auto it = std:: remove_if ( c. begin ( ) , c. end ( ) , pred ) ;
auto r = std:: distance ( it, c. end ( ) ) ;
c. erase ( it, c. end ( ) ) ;
return r ; 。

目录

参数

c - 要执行擦除操作的容器
value - 待移除的数值
pred - 一元谓词，当元素应被擦除时返回​ true 。

表达式 pred ( v ) 必须可转换为 bool ，其中参数 v 为类型（可能为 const） T ，且不受 值类别 影响，同时不得修改 v 。因此不允许使用 T & 作为参数类型 ， T 也不允许，除非对于 T 类型移动操作等同于复制操作 (C++11 起) 。 ​

返回值

被擦除的元素数量。

复杂度

线性。

示例

运行此代码 
#include <cassert>
#include <complex>
#include <inplace_vector>
#include <numeric>
#include <print>
int main()
{
    std::inplace_vector<int, 10> v(10, 0);
    std::ranges::iota(v, 0);
    std::println("Initially, v = {}", v);
    auto erased = std::erase(v, 3);
    std::println("After erase(v, 3), v = {}", v);
    assert(erased == 1);
    erased = std::erase_if(v, [](int x) { return x % 2 == 0; });
    std::println("After erasing all even numbers, v = {}", v);
    std::println("Erased even numbers: {}", erased);
    std::inplace_vector<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}};
    std::erase(nums, {4, 2}); // since U = T, the value type can be ommited
    std::println("After erase {4, 2}, nums = {}", nums);
}

输出： 

Initially, v = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
After erase(v, 3), v = [0, 1, 2, 4, 5, 6, 7, 8, 9]
After erasing all even numbers, v = [1, 5, 7, 9]
Erased even numbers: 5
After erase {4, 2}, nums = [(2,2), (4,8)]

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)