java 实现 快速查找算法 QuickSelect，

public class QuickSelect {
	
	private static Comparable median3(Comparable[] data , int left, int right){
		int center = (left + right) /2 ;
		if(data[center].compareTo(data[left]) < 0)
			swapReferences(data, left, center);
		if(data[right].compareTo(data[left]) < 0)
			swapReferences(data, left, right);
		if(data[right].compareTo(data[center]) < 0)
			swapReferences(data, center, right);
		swapReferences(data, center, right -1);
		
		return data[right - 1];
		
	}
	
	private static void swapReferences(Comparable[] data, int src, int des){
		Comparable tmp;
		tmp = data[des];
		data[des] = data[src];
		data[src] = tmp;
	}
	
	private static void  quickSelect(Comparable[] data, int left, int right, int k){
		if(left + CUTOFF <= right){
			Comparable pivot = median3(data, left, right);
			
			int i = left;
			int j= right -1;
			for(; ;){
				while(data[++i].compareTo(pivot) < 0){}
				while(data[--j].compareTo(pivot) > 0) {}
				
				if(i < j)
					swapReferences(data, i, j);
				else
					break;
			}
			
			swapReferences(data, i, right - 1);
			
			if(k <= i){
				quickSelect(data,left, i - 1, k);
				//return data[left+k-1];
			}
			else{
				quickSelect(data, i + 1, right, k);
				//return data[left + k -1];
			
			}
		}
		else{
			insertionSort(data, left, right);
			//return data[left + k -1];
		}
	}
	
	private static void insertionSort(Comparable[] data, int left, int right){
		int j;
		for(int p = left + 1; p <= right; p++){
			Comparable tmp = data[p];
			for(j = p; j > left && tmp.compareTo(data[j-1]) < 0; j--)
				data[j] = data[j-1];
			data[j] = tmp;
				
		}
	}
	
	public static Comparable quickSelect(Comparable[] data, int k){
		
		quickSelect(data, 0, data.length - 1, k);
		return data[k -1];
		
	}
	
	
	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);
		for(int i = 0; i < a.length; i ++)
			System.out.print(a[i] + ", ");
		System.out.println("//");
		Comparable b =  quickSelect(a, 8);
		for(int i = 0; i< a.length; i++)
			System.out.print(a[i] +", ");
		System.out.println("//");
		System.out.println(b);
	}
	
	private final static int CUTOFF = 10;

}

5, 8, 37, 72, 67, 64, 60, 32, 0, 95, 43, 3, 7, 16, 11, 75, 29, 54, 41, 13, //
5, 8, 11, 7, 3, 0, 13, 16, 29, 32, 43, 67, 72, 60, 37, 75, 64, 54, 41, 95, //
16