题目： 代码：
class Solution { public: int search(vector<int>& nums, int target) { int begin=0,end=nums.size()-1; int mid; while(begin<=end){ mid=begin+(end-begin)/2; if(nums[mid]==target) return mid; else if(nums[mid]>target) end=mid-1; else begin=mid+1; } return -1; } };注意begin<end和begin<=end这两种情况的区别即可
