C++ STL copy_if 用法

一：功能

将容器中满足给定条件的元素拷贝到另一个容器中

二：用法

#include <iostream>
#include <vector>
#include <utility>
#include <algorithm>

int main() {
    std::vector<int> data{ 1, 2, 3, 4, 5, 6, 7, 8, 9};
    std::vector<int> even;

    auto is_even = [](int v) { return v % 2 == 0; };

    std::ranges::copy_if(data, std::back_inserter(even), is_even);
    std::cout << "even == {";
    std::string delim;
    for (auto v : even)
        std::cout << std::exchange(delim, ", ") << v;
    std::cout << "}\n";
}