378.leetcode Kth Smallest Element in a Sorted Matrix(medium)[堆求第K小的 ]

Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix.

Note that it is the kth smallest element in the sorted order, not the kth distinct element.

Example:

matrix = [   [ 1,  5,  9],   [10, 11, 13],   [12, 13, 15]],k = 8,return 13.

采用堆的思想来做，这个堆存放一个K个元素的最大堆，堆顶元素元素就是所求

class Solution {public:    //采用堆的思想来做，这个堆存放一个K个元素的最大堆，堆顶元素元素就是所求    int kthSmallest(vector<vector<int>>& matrix, int k) {        if(matrix.size()<=0) return 0;        priority_queue<int> ipq;        for(int i = 0;i<matrix.size();i++)            for(int j = 0;j<matrix[i].size();j++)            {                ipq.push(matrix[i][j]);                if(ipq.size()>k)                     ipq.pop();            }        return ipq.top();    }};