Guess Number Higher or Lower.java

//374. Guess Number Higher or Lower
/** 
 * Forward declaration of guess API.
 * @param  num   your guess
 * @return 	     -1 if num is higher than the picked number
 *			      1 if num is lower than the picked number
 *               otherwise return 0
 * int guess(int num);
 */

public class Solution extends GuessGame {
  public int guessNumber(int n) {
    int l = 1;
    int r = n;

    // Find the first guess num that >= target num
    while (l < r) {
      final int m = l + (r - l) / 2;
      if (guess(m) <= 0) // -1, 0
        r = m;
      else
        l = m + 1;
    }

    return l;
  }
}