折半查找，二分查找，

//折半查找，二分查找，
public class BinarySearch {
	
	public static int binarySearch(int[] a, int x){
	
		int low = 0;
		int high = a.length - 1;
		
		while(low <= high){
			
			int mid = (low + high) / 2;
			if(a[mid] > x)
				high = mid - 1;
			else if(a[mid] < x)
				low = mid + 1;
			else
				return mid;
			
			
		}
		return -1;
		
		
	}
	
	public static void main(String[] args){
	
		int[] b = {1,5,6,7,8,9,12,46,166,544,44444};
		//int x = 646;
		int x = 12;
		int index = binarySearch(b,x);
		System.out.println(x +"  b["+ index +"] = "+ b[index]);
	}

}