Merge pull request #488 from sneekr-a/patch-1

Create priorityqueue_sort.cpp

Author: amritansh22

SortingAlgorithms/priorityqueue_sort.cpp

@@ -0,0 +1,40 @@
+#include <queue> // for priority_queue on line 7
+#include <vector> // for vector on line 5
+
+/* Problem
+Given a reference to a vector of values, sort the vector using a pqSort.
+*/
+
+template <typename T>
+void pqSort(std::vector<T>& v)
+{
+   
+   //Step 1) Define a priority queue such that the ordering uses std::greater
+   std::priority_queue<T, std::vector<T>, std::greater<T>> pq;
+   
+   //Step 2) Push all values in the vector onto the priority queue
+   while(!v.empty())
+   {
+      pq.push(v.back());
+      v.pop_back();
+   }
+   
+   //Step 3) Pop all vlaues in the priority queue onto the vector
+   //        - Because the priority queue uses the std::greater ordering function
+   //        - to decide where to insert the value in the tree to maintain increasing
+   //        - order, the least value is stored at the top always.
+   while(!pq.empty())
+   {
+      v.emplace_back(pq.top());
+      pq.pop();
+   }
+   
+}
+
+/* Notes
+ - pqSort is a relatively efficient and rarely mentioned, since it moreso demonstrates the quality of priority queues to sort at insertion.
+ - > and also because faster sorting algorithms exist.
+ - If studying DS&A, this is a good example of priority queues primary functionality.
+ - You can write your own comparison function to use on your own datatypes, etc, and implement them painlessly.
+ - > for more info on how to do that, check out std::greater
+*/