374. Guess Number Higher or Lower

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Total Accepted: 46483
Total Submissions: 133710
Difficulty: Easy
Contributor: LeetCode

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.

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(E) First Bad Version (M) Guess Number Higher or Lower II

/* 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 start = 0, end = n;
      while (start <= end) {
          int mid = start + (end - start) / 2;
          int val = guess(mid);
          if (val == 0) {
              return mid;
          } else if (val == -1) {
              end = mid - 1;
          } else if (val == 1) {
              start = mid + 1;
          }
      }
       return start; 
    }
}