/**
 * @author dx
 * @version 1.0
 * @date 2022年3月20日 21:03
 * @description:
 */
public class Dichotomy {
 public static void main(String args[]){
 int[] nums = {1,2,4,5,6,7,23,24};
 int found = search1(nums,6);
 System.out.println(found);
 }
 //左闭右闭区间
 public static int search1(int[] nums, int target){
 int left = 0,right = nums.length-1;
 while (left <= right){
 int mid = left+((right-left)>>1); //防止溢出
 if (nums[mid] == target)
 return mid;
 else if (nums[mid] > target)
 right = mid -1;
 else if (nums[mid] < target)
 left = left+1;
 }
 return -1;
 }
 /*while(left<right)这里使用<,left == right在区间[left,right)是没有意义的,
 if(nums[middle]>target),right更新为middle,因为当前nums[middle]不等于target,去左区间查找,而左区间是左闭右开,所以更新right为middle
 */
 public static int search2(int[] nums,int target){
 int left = 0,right = nums.length-1;
 while(left < right){
 int mid = left + ((right-left)>>1);
 if(nums[mid] == target)
 return mid;
 else if (nums[mid] > target )
 right = mid;
 else if (nums[mid] < target )
 left = mid+1;
 }
 return -1;

 }
}