堆排序

参考: http://blog.youkuaiyun.com/chenjin_zhong/article/details/6045892

package sort;

import java.util.Arrays;

public class HeapSort {

	public static void main(String[] args) {
		int[] a = {7, 23, 78, 21, 23 ,34, 233,254};
		buildHeap(a);
		System.out.println(Arrays.toString(a));
		sortHeap(a);
		System.out.println(Arrays.toString(a));
	}

	private static void sortHeap(int[] a) {
		// TODO Auto-generated method stub
		for(int i = a.length - 1; i > 0; i--){
			int tmp = a[i];
			a[i] = a[0];
			a[0] = tmp;
			adjustHeap(a, 0, i - 1);
		}
	}

	private static void buildHeap(int[] a) {
		// TODO Auto-generated method stub
		int len = a.length - 1;
		for(int i = len / 2; i >= 0; i--){
			adjustHeap(a, i, len);
		}
	}

	private static void adjustHeap(int[] a, int i, int len) {
		// TODO Auto-generated method stub
		if(len == 0)
			return;
		int target = a[i];
		for(int j = 2*i; j <= len; j*=2){
			
			if(j < len && a[j + 1] > a[j])
				j = j + 1;
			if(target > a[j])
				break;
			a[i] = a[j];
			i = j;
		}
		a[i] = target;
	}
	
}