LeetCode:378. 有序矩陣中第K小的元素

class Solution {
public:
    int kthSmallest(vector<vector<int>>& matrix, int k) {
        priority_queue<int, vector<int>> q;
        for(int i=0;i<matrix.size();i++)
        {
            for(int j=0;j<matrix[i].size();j++)
            {
                q.push(matrix[i][j]);
                if(q.size()>k)
                {
                    q.pop();
                }
            }
        }
        return q.top();
    }
};