二分法查找

package com.abstractdatatype.search;
/*二分法查找*/
public class BinarySearch {

	public static void main(String[] args) {
		
		int [] a=new int [] {1,2,3,4,5,7,8,9}; 
		int index=BinarySearch.binarySearch(a, 7);
		System.out.println(index);
		
	}
	
	/*Performs the standard binary search
	 * @return index where item is found, or -1 if not found 
	 * */
	public static int binarySearch(int [] a,int target){
		final int NOT_FOUND=-1;
		int low=0;
		int high=a.length-1;
		while(low<high){
			int mid=(low+high)/2;
			if(a[mid]<target){
				low=mid+1;
			}else if(a[mid]>target){
				high=mid-1;
			}else{
				return mid;
			}
		}
		return NOT_FOUND;
	}
}