2-二分查找

方法一：

左闭右闭，[left, right]

class Solution {
public:int search(vector<int>& nums, int target) {//[left, right]int left = 0;int right = nums.size() - 1 ;while(left <= right){int middle = left + ((right - left) / 2);if(nums[middle] > target){right = middle - 1;}else if(nums[middle] < target){left = middle + 1;}else{return middle;}}return -1;}
};

方法二：

左闭右闭，[left, right]

class Solution {
public:int search(vector<int>& nums, int target) {int left = 0;int right = nums.size();while(left < right){int middle =  left + ((right - left) >> 1);if(nums[middle] > target){right = middle;}else if (nums[middle] < target){left = middle + 1;}else { return middle; }}return -1;}
};

链接