/*
  Heap Sort
  Implementation of Heap Sort in Java which uses max heap
*/

public class HeapSort
{
    public void sort(int arr[])
    {
        int n = arr.length;

        // Step 1: Build heap (rearrange array)
        for (int i = n / 2 - 1; i >= 0; i--)
            heapify(arr, n, i);

        // Step 2: Extract elements one by one from heap
        for (int i=n-1; i>=0; i--)
        {
            // Step 2.1: Move current root to end
            int temp = arr[0];
            arr[0] = arr[i];
            arr[i] = temp;

            // Step 2.2: Call max heapify on the reduced heap
            heapify(arr, i, 0);
        }
    }
    /*  Method to heapify a subtree rooted with node i which is

        an index in arr[].
        Heap Size = n
    */
    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 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)
        {
            int swap = arr[i];
            arr[i] = arr[largest];
            arr[largest] = swap;

            // Recursively heapify the affected sub-tree
            heapify(arr, n, largest);
        }
    }

    /* A utility function to print array of size n */
    static void printArray(int arr[])
    {
        int n = arr.length;
        for (int i=0; i<n; ++i)
            System.out.print(arr[i]+" ");
        System.out.println();
    }

    // Driver program
    public static void main(String args[])
    {
        int arr[] = {19, 13, 15, 8, 9, 7};
        int n = arr.length;

        HeapSort ob = new HeapSort();
        ob.sort(arr);

        System.out.println("Sorted array is");
        printArray(arr);
    }
}