HeapSort.java

/**
 * HeapSort
 */
public class HeapSort {
    public void sort(int arr[])
    {
        int n = arr.length;
    
        for (int i = n / 2 - 1; i >= 0; i--)
            heapify(arr, n, i);
    
        for (int i = n - 1; i > 0; i--) {
            // Move current root to end
            int temp = arr[0];
            arr[0] = arr[i];
            arr[i] = temp;

            heapify(arr, i, 0);
        }
    }

    void heapify(int arr[], int n, int i)
    {
        int largest = i; // Initialize largest as root
        int l = 2 * i + 1; // left = 2*i + 1
        int r = 2 * i + 2; // right = 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 swap = arr[i];
            arr[i] = arr[largest];
            arr[largest] = swap;

            heapify(arr, n, largest);
        }
    }
    static void printArray(int arr[])
    {
        int n = arr.length;
        for (int i = 0; i < n; ++i)
            System.out.print(arr[i] + " ");
        System.out.println();
    }
    
    public static void main(String args[])
    {
        int arr[] = { 92, 15, 83, 5, 60, 17 };
        int n = arr.length;
    
        HeapSort ob = new HeapSort();
        ob.sort(arr);
    
        System.out.println("Sorted array is");
        printArray(arr);
    }
    
}