while方式
package com.sitech.iot.monitor.controller;
public class demo {
public static int search(int[] nums, int target) {
int l=0,r=nums.length-1;
if(r==-1)
return -1;
while(l<=r){
int mid=l+(r-l)/2;
if(nums[mid]>target)
r=mid-1;
else if(nums[mid]<target)
l=mid+1;
else return mid;
}
return -1;
}
public static void main(String[] args){
int[]a={1,2,4,5,8};
System.out.println(search(a,5));
}
}
递归实现:
/**
* 使用递归的二分查找
*title:recursionBinarySearch
*@param arr 有序数组
*@param key 待查找关键字
*@return 找到的位置
*/
public static int recursionBinarySearch(int[] arr,int key,int low,int high){
if(key < arr[low] || key > arr[high] || low > high){
return -1;
}
int middle = (low + high) / 2; //初始中间位置
if(arr[middle] > key){
//比关键字大则关键字在左区域
return recursionBinarySearch(arr, key, low, middle - 1);
}else if(arr[middle] < key){
//比关键字小则关键字在右区域
return recursionBinarySearch(arr, key, middle + 1, high);
}else {
return middle;
}
}