LintCode 堆化代码

public class Solution {
    /**
     * @param A: Given an integer array
     * @return: void
     */
    private void siftdown(int[] A, int k) {
        while (k < A.length) {
            int smallest = k;
            if (k * 2 + 1 < A.length && A[k * 2 + 1] < A[smallest]) {
                smallest = k * 2 + 1;
            }
            if (k * 2 + 2 < A.length && A[k * 2 + 2] < A[smallest]) {
                smallest = k * 2 + 2;
            }
            if (smallest == k) {
                break;
            }
            int temp = A[smallest];
            A[smallest] = A[k];
            A[k] = temp;
            
            k = smallest;
        }
    }
    
    public void heapify(int[] A) {
        for (int i = A.length / 2; i >= 0; i--) {
            siftdown(A, i);
        } 
    }
}