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// Java program for implementation of Heap Sort

public class HeapSort {

public void sort(int arr[])

{

int n = arr.length;

// 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

int temp = arr[0];

arr[0] = arr[i];

arr[i] = temp;

// call max heapify on the reduced heap

heapify(arr, i, 0);

}

}

// 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

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 code

public static void main(String args[])

{

int arr[] = { 12, 11, 13, 5, 6, 7 };

int n = arr.length;

HeapSort ob = new HeapSort();

ob.sort(arr);

System.out.println("Sorted array is");

printArray(arr);

}

}