Heapify

 1 public class Solution {
 2     /**
 3      * @param A: Given an integer array
 4      * @return: void
 5      */
 6 
 7     public void heapify(int[] array) {
 8         int heapSize = array.length;
 9         for (int i = heapSize / 2 - 1; i >= 0; i--) {
10             minHeapify(array, i, array.length);
11         }
12     }
13     
14     /// MaxHeapify is to build the max heap from the ‘position‘
15     public void minHeapify(int[] array, int position, int heapSize)
16     {
17         int left = left(position);
18         int right = right(position);
19         int minPosition = position;
20         
21         if (left < heapSize && array[left] < array[position]) {
22             minPosition = left;
23         }
24         
25         if (right < heapSize && array[right] < array[minPosition]) {
26             minPosition = right;
27         }
28         
29         if (position != minPosition) {
30             swap(position, minPosition, array);
31             minHeapify(array, minPosition, heapSize);
32         }
33     }
34     
35     public void swap(int i, int j, int[] A) {
36         int temp = A[i];
37         A[i] = A[j];
38         A[j] = temp;
39     }
40     
41     /// return the left child position
42     public int left(int i)
43     {
44         return 2 * i + 1;
45     }
46     /// return the right child position
47     public int right(int i)
48     {
49         return 2 * i + 2;
50     } 
51 }