topK问题,用一个大小为K的堆实现。

class Solution {
public:
    vector<int> GetLeastNumbers_Solution(vector<int> input, int k) {
        vector<int> result{};
        if(k==0) return result;
        
        priority_queue<int,vector<int>,less<int>> max_heap{};
        for(int i=0;i<k;i++){
            max_heap.push(input[i]);
        }
        for(int i=k;i<input.size();++i){
            if(input[i]<max_heap.top()){
                max_heap.pop();
                max_heap.push(input[i]);
            }
        }
        
        while(!max_heap.empty()){
            result.push_back(max_heap.top());
            max_heap.pop();
        }
        return result;
    }
};