std::unordered_set<Key,Hash,KeyEqual,Allocator>:: count

#include <algorithm>
#include <iostream>
#include <unordered_set>
int main()
{
    std::unordered_set set{2, 7, 1, 8, 2, 8, 1, 8, 2, 8};
    std::cout << "集合内容为: ";
    for (int e : set)
        std::cout << e << ' ';
    const auto [min, max] = std::ranges::minmax(set);
    std::cout << "\n从 " << min << " 到 " << max << " 范围内存在于集合中的数字: ";
    for (int i{min}; i <= max; ++i)
        if (set.count(i) == 1)
            std::cout << i << ' ';
    std::cout << '\n';
}