374. Guess Number Higher or Lower

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LeetCode

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Problem

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 will tell you whether the number I picked is higher or lower than your guess.

You call a pre-defined API int guess(int num), which returns 3 possible results:

• -1: The number I picked is lower than your guess (i.e. pick < num).
• 1: The number I picked is higher than your guess (i.e. pick > num).
• 0: The number I picked is equal to your guess (i.e. pick == num).

Return the number that I picked.

Code

/**
 * 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);
 */

class Solution extends GuessGame {
    public int guessNumber(int n) {
        int left = 1;
        int right = n;

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

        if(guess(left) == 0) return left;
        if(guess(right) == 0) return right;

        return -1;
    }
}