LeetCode - Guess Number Higher or Lower

LiBlog發表於2016-07-18

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.


Solution:

 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 low = 1;
 9         int high = n;
10         
11         while (low<=high){
12             int mid = (high-low)/2 + low;
13             int res = guess(mid);
14             if (res == 0){
15                 return mid;
16             } else if (res == -1) {
17                 high = mid-1;
18             } else {
19                 low = mid+1;
20             }
21         }
22         
23         return -1;
24     }
25 }

 

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