278. First Bad Version

// Forward declaration of isBadVersion API.
bool isBadVersion(int version);

class Solution 
{
public:
    int firstBadVersion(int n) 
    {
        int left=1,right=n;
        while(left<right)
        {
            int mid=left+(right-left)/2;
            if(isBadVersion(mid))
                right=mid;
            else
                left=mid+1;
        }
        return left;
        
    }
};

这题使用二分查找，注意二分查找很容易出问题，十个二分九个错。