一、二分查找法是什么?

给定一个 n 个元素有序的（升序）整型数组 nums 和一个目标值 target，返回target在数组中的下标

二、二分查找法易错点

临界点容易弄错

while(left < right) 亦或者  while(left <= right) if(nums[middle] > target){right = middle 亦或者 right = middle - 1
}

三、如何解决上述提到的问题

看循环的条件变量是否在你定义的区间内

当 区间为 [1,1] 时，看 while(1<= 1) 是否满足条件，满足的话则是while(left <= right) ，不满足的话则是while(left < right)
当 区间为 [1,1）时，看 while(1<= 1) 是否满足条件，满足的话则是while(left <= right) ，不满足的话则是while(left < right)

四、左闭右闭写法

public class BinarySearch {public int search(int[] nums, int target) {int left = 0, right = nums.length - 1, middle;while (left <= right) {middle = (left + right) / 2;if (nums[middle] > target) {right = middle - 1;} else if (nums[middle] < target) {left = middle + 1;} else {return middle;}}return -1;}public static void main(String[] args) {BinarySearch binarySearch = new BinarySearch();int[] nums = {-1, 0, 3, 5, 9, 12};System.out.println(binarySearch.search(nums, 5));}
}

五、左闭右开写法

public class BinarySearch {public int search(int[] nums, int target) {int left = 0, right = nums.length , middle;while (left < right) {middle = (left + right) / 2;if (nums[middle] > target) {right = middle ;} else if (nums[middle] < target) {left = middle + 1;} else {return middle;}}return -1;}public static void main(String[] args) {BinarySearch binarySearch = new BinarySearch();int[] nums = {-1, 0, 3, 5, 9, 12};System.out.println(binarySearch.search(nums, 5));}
}