2025-09-12 Daily Challenge

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In: DailyChallenge

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

September LeetCoding Challenge 12

Description

Vowels Game in a String

Alice and Bob are playing a game on a string.

You are given a string s, Alice and Bob will take turns playing the following game where Alice starts first:

  • On Alice's turn, she has to remove any non-empty substring from s that contains an odd number of vowels.
  • On Bob's turn, he has to remove any non-empty substring from s that contains an even number of vowels.

The first player who cannot make a move on their turn loses the game. We assume that both Alice and Bob play optimally.

Return true if Alice wins the game, and false otherwise.

The English vowels are: a, e, i, o, and u.

 

Example 1:

Input: s = "leetcoder"

Output: true

Explanation:
Alice can win the game as follows:

  • Alice plays first, she can delete the underlined substring in s = "leetcoder" which contains 3 vowels. The resulting string is s = "der".
  • Bob plays second, he can delete the underlined substring in s = "der" which contains 0 vowels. The resulting string is s = "er".
  • Alice plays third, she can delete the whole string s = "er" which contains 1 vowel.
  • Bob plays fourth, since the string is empty, there is no valid play for Bob. So Alice wins the game.

Example 2:

Input: s = "bbcd"

Output: false

Explanation:
There is no valid play for Alice in her first turn, so Alice loses the game.

 

Constraints:

  • 1 <= s.length <= 105
  • s consists only of lowercase English letters.

Solution

class Solution {
  bool isVowel(char c) {
    switch(c) {
      case 'a':
      case 'e':
      case 'i':
      case 'o':
      case 'u':
        return true;
      default:
    }
    return false;
  }
public:
  bool doesAliceWin(string s) {
    int count = 0;
    for(auto c : s) {
      if(isVowel(c)) return true;
    }
    return false;
  }
};

// Accepted
// 697/697 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 53.73 % of cpp submissions (19.1 MB)
Algorithm