adding priority queue problem

leetcode/p378_kth_smallest_in_matrix.cpp

@@ -0,0 +1,18 @@
+class Solution {
+public:
+    int kthSmallest(vector<vector<int>>& matrix, int k) {
+        std::priority_queue<int> my_pq;
+        int size = matrix.size();
+        for(int i=0;i<size;i++){
+            for(int j=0;j<size;j++){
+                my_pq.push(matrix[i][j]);
+                // doing so guarantees that there are only k elements in the priority queue; and we always kick the largest one out.
+                if(my_pq.size()>k){
+                    my_pq.pop();
+                }
+            }
+        }
+        // when we get out of the above nested loops, we know the priority queue stores the k smallest elements, and at the top is the largest element among them.
+        return my_pq.top();
+    }
+};