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LeetCode 374. Guess Number Higher or Lower

We are playing the Guess Game. The game is as follows:

 

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I‘ll tell you whether the number is higher or lower.

You call a pre-defined API guess(int num) which returns 3 possible results (-11, or 0):

-1 : My number is lower 1 : My number is higher 0 : Congrats! You got it!

Example:

n = 10, I pick 6.Return 6.

 

 

  一个二分查找

// Forward declaration of guess API.// @param num, your guess// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0int guess(int num);class Solution {public:    int guessNumber(int n) {        long long start=1,end=n;        long long mid=(start+end+1)/2;        if(0==guess(start))return start;        while(guess(mid))        {            if(-1==guess(mid))            {                end=mid-1;                mid=(start+end+1)/2;            }            if(1==guess(mid))            {                start=mid+1;                if(0==guess(start))return start;                mid=(start+end+1)/2;            }        }        return mid;    }};

 

LeetCode 374. Guess Number Higher or Lower