374-guess-number-higher-or-lower

Question

https://leetcode.com/problems/guess-number-higher-or-lower/description/

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.

Thought Process

1. Binary Search
   1. Very Typical binary search, where we return when we get 0, search the lower half when we got -1 (the solution is lower), otherwise we search the higher half
   2. Time complexity O(nlogn)
   3. Space complexity O(1)

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 lo = 0, hi = n;
        int mid;
        while (lo <= hi) {
            mid = lo + (hi - lo)/2;
            int g = guess(mid);
            if (g == 0) return mid;
            else if (g > 0) lo = mid + 1;
            else hi = mid - 1;
        }
        return -1;
    }
}

Additional