堆排序

public class HeapSort {
	
	public void sort(int[] a) throws Exception {
		if((a==null) || (a.length==0)){
			throw new Exception();
		}
		build(a);
		run(a);
	}
	
	private void build(int[] a){
		int size = a.length/2 -1;
		for(int i=size; i>=0; i--){
			ajust(a, i, a.length);
		}
	}
	
	private void ajust(int[] a, int parent, int length){
		if(parent > (length/2 -1)){
			return;
		}
		int left_child = 2*parent +1;
		int right_child = 2*parent +2;
		if(right_child == length){
			if(a[parent] > a[left_child]){
				swap(a, left_child, parent);
			}
			return;
		}
		int min = a[left_child] < a[right_child] ? a[left_child] : a[right_child];
		if(a[parent] > min){
			if(a[left_child] < a[right_child]){
				swap(a, left_child, parent);
				ajust(a, left_child, length);
			}else{
				swap(a, right_child, parent);
				ajust(a, right_child, length);
			}
		}
	}
	
	private void run(int[] a){
		int i = a.length - 1;
		while(i>0){
			swap(a, 0, i);
			ajust(a, 0, i);
			i--;
		}
	}
	
	private void swap(int[] a, int p1, int p2){
		int temp = a[p1];
		a[p1] = a[p2];
		a[p2] = temp;
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int[] a = {7,2,4,8,3,5,1,9,0,6};
		HeapSort hs = new HeapSort();
		try {
			hs.sort(a);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		Tools.printArray(a);

	}

}