2021-10-12 Daily-Challenge

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Today I have done leetcode's October LeetCoding Challenge with cpp.

October LeetCoding Challenge 12

Description

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 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:

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

Constraints:

  • 1 <= n <= 231 - 1
  • 1 <= pick <= n

Solution

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

// Accepted
// 25/25 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 67.31 % of cpp submissions (5.9 MB)
Algorithm