374. Guess Number Higher or Lower

// Forward declaration of guess API.
// @param num, your guess
// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
int guess(int num);

class Solution 
{
public:
    int guessNumber(int n) 
    {
        int left=1,right=n,mid=0;
        while(left<right)
        {
            mid=left+(right-left)/2;
            if(guess(mid)==1)
                left=mid+1;
            else if(guess(mid)==-1)
                right=mid;
            else
                return mid;
        }
        return left;
    }
};

二分，问题不大