Question

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 :

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

Difficulty:Easy

Category:Binary-Search

Analyze

Solution

// Forward declaration of guess API.
// @param num, your guess
// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
int guess(int num);

class Solution {
 public:
  int guessNumber(int n) {
    long int left = 1, right = n;
    while (left <= right) {
      long int mid = (left + right) / 2;
      int res = guess(mid);
      if (!res)
        return mid;
      else if (res == 1)
        left = mid + 1;
      else
        right = mid;
    }
    return left;
  }
};