优先队列

c++优先队列priority_queue（自定义比较函数）_c++优先队列自定义比较-CSDN博客

373. 查找和最小的 K 对数字 - 力扣（LeetCode）

官方题解：

class Solution {
public:
    vector<vector<int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k) {
        auto cmp = [&nums1,&nums2](const pair<int,int>& a,const pair<int,int>& b) {
            return nums1[a.first] + nums2[a.second] > nums1[b.first] + nums2[b.second];
        };
        int m = nums1.size();
        int n = nums2.size();
        vector<vector<int>> ans;
        priority_queue<pair<int,int>,vector<pair<int,int>>,decltype(cmp)> pq(cmp);
        for(int i = 0;i < min(k,m);i++) {
            pq.emplace(i,0);
        }
        while(k-- > 0 && !pq.empty()) {
            auto [x,y] = pq.top();
            pq.pop();
            ans.emplace_back(initializer_list<int>{nums1[x],nums2[y]});
            if(y + 1 < n) {
                pq.emplace(x,y + 1);
            }
        }
        return ans;
    }
};

c++优先队列(priority_queue)用法详解_c++ 优先队列-CSDN博客

count函数

[C++] 基础教程 - std::count函数介绍和使用场景_std::cout-CSDN博客

std::count 是C++标准库的一个算法，用来计算给定值在指定范围内出现的次数

template <class InputIt, class T>
size_t count(InputIt first, InputIt last, const T& value);

使用场景：

#include <iostream>
#include <vector>
#include <algorithm>
 
int main() {
    std::vector<int> nums = {1, 2, 3, 4, 5, 2, 3, 2};
    int target = 2;
 
    size_t count = std::count(nums.begin(), nums.end(), target);
    std::cout << "The number " << target << " appears " << count << " times in the array." << std::endl;
 
    return 0;
}

#include <iostream>
#include <string>
#include <algorithm>
 
int main() {
    std::string str = "hello world";
    char target = 'l';
 
    size_t count = std::count(str.begin(), str.end(), target);
    std::cout << "The character '" << target << "' appears " << count << " times in the string." << std::endl;
 
    return 0;
}