374. Guess Number Higher or Lower

Problem

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

Solution

public class Solution : GuessGame{
    public int GuessNumber(int n){
        var low = 0;
        var high = n;
        var ret = 0;
        while(low<=high)
        {
            var g = low+(high-low)/2;
            if(guess(g)==0)
            {
                ret=g;
                break;
            }
            if(guess(g)==-1)
                high=g-1;
            else
                log=g+1;
        }
        return ret;
    }
}