[Leetcode]2124. Check if All A's Appears Before All B's

📄 Description

Given a string s consisting of only the characters 'a' and 'b', return true if every 'a' appears before every 'b' in the string. Otherwise, return false.

Example 1:

Input: s = "aaabbb"
Output: true
Explanation:
The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.
Hence, every 'a' appears before every 'b' and we return true.

Example 2:

Input: s = "abab"
Output: false
Explanation:
There is an 'a' at index 2 and a 'b' at index 1.
Hence, not every 'a' appears before every 'b' and we return false.

Example 3:

Input: s = "bbb"
Output: true
Explanation:
There are no 'a's, hence, every 'a' appears before every 'b' and we return true.

Constraints:

• 1 <= s.length <= 100
• s[i] is either 'a' or 'b'.

💻 My Submission

class Solution:
    def checkString(self, s: str) -> bool:
        if 'a' and 'b' in s:
            start_b=s.index('b')
            if 'a' in s[start_b:]:
                return False
        return True

💭 Better Solution(1)

class Solution:
    def checkString(self, s: str) -> bool:
        return "ba" not in s

💭 Better Solution(2)

class Solution:
    checkString = re.compile('a*b*').fullmatch

• fullmatch(): 문자열 전부가 매치되는가를 체크

💡 What I learned

References

• https://leetcode.com/problems/divide-a-string-into-groups-of-size-k/
• https://leetcode.com/problems/check-if-all-as-appears-before-all-bs/discuss/1661056/Python-1-Liner
• https://engineer-mole.tistory.com/189