菜鸟Java大面经----------------关于二分法

关于二分法

package com.ahuiby.demo1;

public class BinarySearch {
	
	//二分法
	public static int binarySearch(int arr[],int key){
		int begin=0;
		int end =arr.length-1;
		
		while(begin<=end){
			if(arr[(begin+end)/2]<key){
				begin=(begin+end)/2+1;
			}else if(arr[(begin+end)/2]==key){
				return (begin+end)/2;
			}else{
				end=(begin+end)/2-1;
			}
		}
		
		return -1;
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int[] arr={1,2,3,4,5,6,7,8,9,10};
		int flag=binarySearch(arr,7);
		
		if(flag==-1){
			System.out.println("列表中无此数！");
		}else{
			System.out.println("该数在数组中的下标为："+flag);
		}
	}

}