java实现 二分查找 非递归与递归2种方式

非递归，利用循环

package file;

import java.util.Scanner;

public class Main {
	public static void search(int[] a,int key){
		int low=0;
		int high=a.length-1;
		int mid;
		while(low<=high){
			mid=(low+high)/2;
			if(a[mid]==key){
				System.out.println(mid);
				return;
			}
			else if(a[mid]>key){
				high=mid-1;
			}
			else{
				low=mid+1;
			}			
		}
		return;
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in=new Scanner(System.in);
		System.out.println("输入数组长度：");	
		int len=in.nextInt();
		System.out.println("输入数组：");
		int[] a=new int[len];
		for(int i=0;i<len;i++){
			a[i]=in.nextInt();
		}
		System.out.println("输入key：");
		int key=in.nextInt();
		search(a,key);
	}

}

递归方法

package file;

import java.util.Scanner;

public class Main {

	public static int search(int[] a,int key,int start,int end){
		if(start>end)
			return -1;
		int mid=(start+end)/2;
		if(a[mid]==key){
			System.out.println(mid);
			return mid;
		}
		else if(a[mid]>key){
			return search(a,key,start,mid-1);
		}
		else{
			return search(a,key,mid+1,end);
		}			
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in=new Scanner(System.in);
		System.out.println("输入数组长度：");	
		int len=in.nextInt();
		System.out.println("输入数组：");
		int[] a=new int[len];
		for(int i=0;i<len;i++){
			a[i]=in.nextInt();
		}
		System.out.println("输入key：");
		int key=in.nextInt();
		System.out.println(search(a,key,0,len-1));
	}

}