diff --git a/heapsort.cpp b/heapsort.cpp new file mode 100644 index 0000000..4d6b977 --- /dev/null +++ b/heapsort.cpp @@ -0,0 +1,80 @@ +// C++ program for implementation of Heap Sort +#include +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