HeapSort | Java program for implementation of Heap Sort ; To heapify a subtree rooted with node i which is an index in arr [ ] . n is size of heap ; Initialize largest as root ; left = 2 * i + 1 ; right = 2 * i + 2 ; If left child is larger than root ; If right child is larger than largest so far ; If largest is not root ; Recursively heapify the affected sub - tree ; The main function to sort an array of given size ; Build heap ( rearrange array ) ; One by one extract an element from heap ; Move current root to end ; call max heapify on the reduced heap ; A utility function to print array of size n ; Driver code
public class HeapSort { 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 swap = arr [ i ] ; arr [ i ] = arr [ largest ] ; arr [ largest ] = swap ; heapify ( arr , n , largest ) ; } } 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 -- ) { int temp = arr [ 0 ] ; arr [ 0 ] = arr [ i ] ; arr [ i ] = temp ; heapify ( arr , i , 0 ) ; } } 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 [ ] = { 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 ) ; } }