374. Guess Number Higher or Lower #

Problem Statement #

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 three possible results:

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

Return the number that I picked.

Example 1:

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

Example 2:

Input: n = 1, pick = 1
Output: 1

Example 3:

Input: n = 2, pick = 1
Output: 1

Constraints:

• 1 <= n <= 231 - 1
• 1 <= pick <= n

Solution: #

impl Solution {
    unsafe fn guessNumber(n: i32) -> i32 {
        let (mut left, mut right) = (1, n);

        while left < right {
            let mid = left + (right - left) / 2;

            if guess(mid) == 1 {
                left = mid + 1;
            } else {
                right = mid;
            }
        }

        left
    }
}

... #