374. Guess-Number-Higher-or-Lower

difficulty: Easy

section pre{ background-color: #eee; border: 1px solid #ddd; padding:10px; border-radius: 5px; }

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 :

Input: n = 10, pick = 6
Output: 6

Method One

/** 
 * Forward declaration of guess API.
 * @param  num   your guess
 * @return       -1 if num is lower than the guess number
 *                1 if num is higher than the guess number
 *               otherwise return 0
 * int guess(int num);
 */
​
public class Solution extends GuessGame {
    public int guessNumber(int n) {
        int left = 1;
        int right = Integer.MAX_VALUE;

        while(left <= right) {
            int pivot = left + (right - left)/2;
            if( guess(pivot) == 1) {
                left = pivot + 1;
            }
            if( guess(pivot) == -1 ) {
                right = pivot - 1;
            }
            if( guess(pivot) == 0) {
                return pivot;
            }
         }
        return -1;
    }
}
​