HeapSort 堆排序算法Java实现

public class HeapSort {
	private static int leftChild(int i){
		return 2 * i + 1;
	}
	
	private static void percDown(Comparable[] data, int i, int n){
		int child;
		Comparable tmp;
		
		for(tmp = data[i]; leftChild(i) < n; i = child){
			child = leftChild(i);
			if(child != n - 1 && data[child].compareTo(data[child + 1]) < 0)
				child ++;
			if(tmp.compareTo(data[child]) < 0)
				data[i] = data[child];
			else 
				break;
		}
		data[i] = tmp;
	}
	
	private static void swapReferences(Comparable[] a, int src, int des){
		Comparable tmp = a[des];
		a[des] = a[src];
		a[src] = tmp;
	}
	
	public static void heapsort(Comparable[] a){
		
		for(int i = a.length / 2; i >= 0; i --)
			percDown(a, i, a.length);
		for(int i = a.length - 1; i > 0; i--){
			swapReferences(a, 0, i);
			percDown(a, 0, i);
		}
			
	}
	
	public static void main(String[] args){
		Comparable[] a = new Comparable[20];
		for(int i = 0; i < a.length; i++){
			a[i] = (int)(Math.random() * 100);
		}
		
		System.out.println("the Before!");
		for(int i = 0; i < a.length; i++)
			System.out.print(a[i] +",");
		
		System.out.println("");
		heapsort(a);
		for(int i = 0; i< a.length; i ++)
			System.out.print(a[i]+ ",");
	}

}