package com.lxf.demo03;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * 二分查找数组中对应值的下标
 * 针对的是有序数组，快速查找
 */
public class BinSearch {
    public static void main(String[] args) throws IOException {
        int[] a=new int[]{1,2,3,4,5,6,7,8,9,10};
        //获取输入的要查找的数
        System.out.println("请输入您要查找的值:");
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        int num = Integer.valueOf(br.readLine());
        //查找这个数
        int i = BinSearch(a, 0, a.length - 1, num);
        if(i>=0){
            System.out.println(num+"值在数组中对应的下标："+i);
        }else{
            System.out.println("该数不存在！");
        }
    }
    public  static int BinSearch(int[] a,int low,int high,int k){
        //中间值
        int mid;
        if(low<=high){
            mid=(low+high)/2;
            if(a[mid]==k){
                //如果中间值等于k，查找结束，返回mid
                return mid;
            }
            if(a[mid]>k){
                //如果a[mid]大于k，查找左区间
                return BinSearch(a, low, mid-1, k);
            }else{
                //如果a[mid]小于k，查找右区间
                return BinSearch(a, mid+1, high,k);
            }
        }else{
            return -1;
        }
    }
}