堆排序

import java.util.Arrays;

public class HeapSort {
	public static void main(String[] args) {
		int[] a = new int[] { 0, 53, 17, 78, 9, 45, 65, 87, 32 };
		heapSort(a, a.length - 1);
		System.out.println(Arrays.toString(a));
	}

	static void heapSort(int[] a, int len) {
		buildMaxHeap(a, len);
		for (int i = len; i > 1; i--) {
			swap(a, i, 1);
			adjustDown(a, 1, i - 1);
		}
	}

	static void swap(int[] a, int i, int j) {
		int temp = a[i];
		a[i] = a[j];
		a[j] = temp;
	}

	static void adjustDown(int[] a, int k, int len) {
		a[0] = a[k];
		for (int i = 2 * k; i <= len; i *= 2) {
			if (i < len // 小於總長度
					&& a[i] < a[i + 1]// k的左右子節點比較
			) {
				i++;
			}
			if (a[0] >= a[i])
				break;
			else {
				a[k] = a[i];
				k = i;// 繼續調整子節點
			}

		}
		a[k] = a[0];
	}

	static void buildMaxHeap(int[] a, int len) {
		for (int i = len / 2; i > 0; i--) {
			adjustDown(a, i, len);
		}
	}
}