原题链接：Leecode 704. 二分查找

代码一：

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

代码二：

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