adding heap sort

lectures/23_priority_queues_II/README.md

@@ -118,4 +118,4 @@ organized heap data, but incur a O(n log n) cost. Why?
 
 ## 23.10 Leetcode Exercises
 
-- [Leetcode problem 912: Sort an Array](https://leetcode.com/problems/implement-queue-using-stacks/). Solution: [p232_queue_using_stacks.cpp](../../leetcode/p232_queue_using_stacks.cpp).
+- [Leetcode problem 912: Sort an Array](https://leetcode.com/problems/sort-an-array/). Solution: [p912_heapsort_array.cpp](../../leetcode/p912_heapsort_array.cpp).

leetcode/p912_heapsort_array.cpp

@@ -0,0 +1,20 @@
+class Solution {
+public:
+    vector<int> sortArray(vector<int>& nums) {
+        vector<int> result;
+        priority_queue<int> pq;
+        int size = nums.size();
+        // build the priority queue, which by default is a max heap
+        for(int i=0;i<size;i++){
+            pq.push(nums[i]);
+        }
+	// pop out the largest element size times
+        for(int i=0;i<size;i++){
+            result.push_back(pq.top());
+            pq.pop();
+        }
+	// sort data in ascending order
+        reverse(result.begin(),result.end());
+        return result;
+    }
+};