Create heapsort.cpp

heapsort.cpp

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+// C++ program for implementation of Heap Sort
+#include <iostream>
+using namespace std;
+
+// To heapify a subtree rooted with node i which is
+// an index in arr[]. n is size of heap
+void heapify(int arr[], int n, int i)
+{
+	int largest = i; // Initialize largest as root Since we are using 0 based indexing
+	int l = 2 * i + 1; // left = 2*i + 1
+	int r = 2 * i + 2; // right = 2*i + 2
+
+	// If left child is larger than root
+	if (l < n && arr[l] > arr[largest])
+		largest = l;
+
+	// If right child is larger than largest so far
+	if (r < n && arr[r] > arr[largest])
+		largest = r;
+
+	// If largest is not root
+	if (largest != i) {
+		swap(arr[i], arr[largest]);
+
+		// Recursively heapify the affected sub-tree
+		heapify(arr, n, largest);
+	}
+}
+
+// main function to do heap sort
+void heapSort(int arr[], int n)
+{
+	// Build heap (rearrange array)
+	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--) {
+		// Move current root to end
+		swap(arr[0], arr[i]);
+
+		// call max heapify on the reduced heap
+		heapify(arr, i, 0);
+	}
+}
+
+/* A utility function to print array of size n */
+void printArray(int arr[], int n)
+{
+	for (int i = 0; i < n; ++i)
+		cout << arr[i] << " ";
+	cout << "\n";
+}
+
+// Driver program
+int main()
+{
+	int arr[] = { 60 ,20 ,40 ,70, 30, 10};
+	int n = sizeof(arr) / sizeof(arr[0]);
+//heapify algorithm
+// the loop must go reverse you will get after analyzing manually
+// (i=n/2 -1) because other nodes/ ele's are leaf nodes
+// (i=n/2 -1) for 0 based indexing
+// (i=n/2) for 1 based indexing
+	for(int i=n/2 -1;i>=0;i--){
+	heapify(arr,n,i);
+}
+
+cout << "After heapifying array is \n";
+	printArray(arr, n);
+
+
+	heapSort(arr, n);
+
+	cout << "Sorted array is \n";
+	printArray(arr, n);
+
+return 0;
+}
+//code by Prajwal Chougale