二分查找 java递归和非递归实现

递归方法

	public static int rank(int []a , int x, int lo, int hi)
	{
		if(hi<lo)
			return -1;
		if(a[lo+(hi-lo)/2]>x)
			return rank(a,x,lo,lo+(hi-lo)/2-1);
		else if(a[lo+(hi-lo)/2]<x) 
			return rank(a,x,lo+(hi-lo)/2+1,hi);
		else
			return a[lo+(hi-lo)/2];	
	}

非递归方法

	public static int rank(int[]a,int key)
	{
		int hi = a.length-1;
		int lo = 0;
		while(lo<=hi) {
			int mid = lo+(hi-lo)/2;
			if (key > a[mid]) lo = mid +1;
			else if (key < a[mid]) hi = mid -1;
			else return a[mid];
		}
		return -1;
	}