Leetcode guessing numbers game - simple

title ：374 Guess the number game - Simple

subject

The rules of the number guessing game are as follows ：

Every round of the game , I'll start from 1 To n Randomly choose a number . Please guess which number is chosen .
If you guessed wrong , I'll tell you , Is your guess larger or smaller than the number I selected .
You can call a predefined interface int guess(int num) To get a guess , The total number of return values is 3 A possible situation （-1,1 or 0）：

-1： The number I picked is smaller than your guess pick < num
1： The number I picked was bigger than you guessed pick > num
0： I picked the same number as you guessed . Congratulations ！ You guessed it ！pick == num
Back to the number 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

Example 4

 Input ：n = 2, pick = 2
 Output ：2

Tips

• 1 <= n <= 231 - 1
• 1 <= pick <= n

Code Java

		public int guessNumber(int n) {
    
        int start = 1;
        int end = n;
        while(start < end) {
    
        //  prevent int overflow 
            int mid = start + (end - start) / 2;
            int x = guess(mid);
            if (x == 0)
                return mid;
            else if (x < 0)
                end = mid - 1;
            else
                start = mid + 1;
        }
        return start;
    }