Guess Number Higher Or Lower Problem


Description

LeetCode Problem 374.

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 3 possible results:

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

Return the number that I picked.

Example 1:

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

Example 2:

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

Example 3:

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

Example 4:

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

Constraints:

  • 1 <= n <= 2^31 - 1
  • 1 <= pick <= n


Sample C++ Code

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

class Solution {
public:
    int guessNumber(int n) {
        int maxNumber = n, minNumber = 1;
        while (true) {
            int meanNumber = (maxNumber - minNumber) / 2 + minNumber;
            int res = guess(meanNumber);
            if (res == 0) { 
                return meanNumber;
            } else if (res == 1) {
                minNumber = meanNumber + 1;
            } else {
                maxNumber = meanNumber - 1;
            }
        }
    }
};




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