heapSort.md

Heap Sort

Usage

make
./heapSort

Code

#include <stdlib.h>
#include <stdio.h>


void heapify(int arr[], int n, int i) {
    int largest = i;
    int l = 2 * i + 1;
    int r = 2 * i + 2;

    if(l < n && arr[l] > arr[largest]) {
        largest = l;
    }

    if(r < n && arr[r] > arr[largest]) {
        largest = r;
    }

    if(largest != i) {
        int temp = arr[i];
        arr[i] = arr[largest];
        arr[largest] = temp;

        heapify(arr, n, largest);
    }
}

void heapSort(int arr[], int n) {
    for(int i = n / 2 - 1; i >= 0; i--) {
        heapify(arr, n, i);
    }

    for(int i = n - 1; i > 0; i--) {
        int temp = arr[0];
        arr[0] = arr[i];
        arr[i] = temp;
        heapify(arr, i, 0);
    }
}

void printArray(int arr[], int n)
{
    for (int i = 0; i < n; ++i) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}
 
// Driver code
int main()
{
    int arr[] = { 12, 11, 13, 5, 6, 7 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    heapSort(arr, n);
    printArray(arr, n);
}

Complexity

Time Complexity: Time complexity of heapify is O(Logn). Time complexity of sorting the heap is O(n) and overall time complexity of Heap Sort is O(nLogn).