374. Guess Number Higher or Lower

Posted 2020-09-01 CodesKiller

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.

本题相对来说比较简单，代码如下：

 1 /* The guess API is defined in the parent class GuessGame.
 2    @param num, your guess
 3    @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
 4       int guess(int num); */
 5 
 6 public class Solution extends GuessGame {
 7     public int guessNumber(int n) {
 8         int left = 1;
 9         int right = n;
10         while(left<right){
11             int mid = left+(right-left)/2;
12             if(guess(mid)==0) return mid;
13             else if(guess(mid)==1) left = mid+1;
14             else right = mid-1;
15         }
16         return left;
17     }
18 }