题目链接

解题思路：

板子题，最基础的二分查找

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