[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 (

-1

, 

1

,
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.

这道题是猜数游戏，题目难度为Easy。

二分查找的题目，比较简单，直接上代码了。具体代码：// 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 bgn = 1, end = n, mid;
while(bgn < end) {
mid = bgn + (end - bgn) / 2;
int rst = guess(mid);
if(rst == 0) return mid;
else if(rst == -1) end = mid - 1;
else bgn = mid + 1;
}
return bgn;
}
};