Merge pull request #1207 from Arpit0324/main

  Heap Sort .cpp

Author: akgmage

sorting/Heap Sort .cpp

@@ -0,0 +1,79 @@
+/*
+Heap sort is a sorting technique based on comparison based on binary heap data.
+Similar to sorting, it finds the largest number first and then puts the largest number last.
+
+
+This sorting algorithm uses a tree structure called the stack, where the stack is a kind of binary tree. 
+A binary decision tree in which the value of the root of a tree is less than or equal to the value of one of its roots is called a min-heap. 
+A decision binary tree is called maximum heap when the value of the root of a tree is greater than or equal to the value of one of its trees. 
+In this post, we'll learn more about C++ Stack Sorting.
+
+Working of heap sort in C++
+To sort any list into a logical order following steps are followed:-
+
+Convert the list into a heap.
+Now convert this heap into a max heap.
+As the heap is converted to max heap largest element in the list is stored in the root of the heap, replace it with the last item of the heap.
+Now delete this node and reduce the size of the heap by 1.
+Follow these steps until the list is sorted.  
+*/
+
+#include<iostream>
+using namespace std;
+void heapify(int arr[], int n, int i){
+    int largest = i;
+    int l = 2*i + 1;
+    int r = 2*i + 2;
+ 
+    //If left child is larger than root
+    if (l < n && arr[l] > arr[largest])
+        largest = l;
+    //If right child largest 
+    if (r < n && arr[r] > arr[largest])
+        largest = r;
+  //If root is nor largest
+    if (largest != i){
+        swap(arr[i], arr[largest]);
+      //Recursively heapifying the sub-tree
+        heapify(arr, n, largest);
+    }
+}
+
+void heapSort(int arr[], int n){
+    for (int i = n / 2 - 1; i >= 0; i--)
+        heapify(arr, n, i);
+  //One by one extract an element from heap
+    for (int i=n-1; i>=0; i--){
+        //Moving current root to end
+        swap(arr[0], arr[i]);
+      //Calling max heapify on the reduced heap
+        heapify(arr, i, 0);
+    }
+}
+ //Function to print array
+void display(int arr[], int n){
+    for (int i = 0; i < n; i++){
+        cout << arr[i] << "\t";
+    }
+    cout << "\n";
+}
+int main(){
+    int arr[] = {1, 14, 3, 7, 0};
+    int n = sizeof(arr)/sizeof(arr[0]);
+    cout << "Unsorted array  \n";
+    display(arr, n);
+    heapSort(arr, n);
+ cout << "Sorted array  \n";
+    display(arr, n);
+}
+
+/*Time Complexcity
+Best
+O(nlog n)
+
+Average
+O(nlog n)
+
+Worst
+O(nlog n)
+*/