LeetCode 374. Guess Number Higher or Lower

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

Initial: Using the Switch and Int Division

- Takes far more time than if and if-else statements.

public class Solution extends GuessGame {
    public int guessNumber(int n) {
        int left= 0;
        int middle = n/2;
        int right = n;
        while (left <= right) {
            middle = left + (right - left)/2;
            System.out.println(middle);
            switch(guess(middle)){
                case -1:
                    right = middle - 1;
                    break;
                case 1:
                    left = middle +1;
                    break;
                default:
                    return middle;
            }
        }
        return middle;
    }
}

Modified Version:

public class Solution extends GuessGame {
    public int guessNumber(int n) {
        int left= 0;
        int right = n;
        int middle = (int)((long)left + ((long)right - (long)left)/2);
        while (left <= right) {            
            int compare = guess(middle);
            if (compare == 0){
                return middle;    
            } else if (guess(right)==0){
                return right;
            } else if (guess(left)==0){
                return left;
            } else if (compare == -1){
                right = middle - 1;
            } else {
                left = middle + 1;
            }
            middle = (int)((long)left + ((long)right - (long)left)/2);
        }
        return middle;
    }
}