题目描述：

方法1：二分查找

注意点：

• middle = (left + right) / 2，最好改为middle = left + ((right - left) / 2)，不然可能会发生溢出

• left <= right，而不是<

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