374. Guess Number Higher or Lower

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.

Solution

/* The guess API is defined in the parent class GuessGame.
   @param num, your guess
   @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
      int guess(int num); */

public class Solution extends GuessGame {
     public int guessNumber(int n) {
     int low=1;
    int high=n;

    while(low <= high){
        int mid = low+((high-low)/2);
        int result = guess(mid);
        if(result==0){
            return mid;
        }else if(result==1){
            low = mid+1;
        }else{
            high=mid-1;
        }
    }

    return -1;
    }

}