[LeetCode] Valid Parentheses

문제

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.

예제

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

Example 4:

Input: s = "([)]"
Output: false

Example 5:

Input: s = "{[]}"
Output: true

조건

• 1 <= s.length <= $10^4$
• s consists of parentheses only '()[]{}'.

답

풀이 1

class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        for i in s:
            if stack:
                if i == ']' and stack[-1] == '[':
                    stack.pop()
                elif i == ')' and stack[-1] == '(':
                    stack.pop()
                elif i == '}' and stack[-1] == '{':
                    stack.pop()
                else:
                    stack.append(i)
            else:
                stack.append(i)
        
        return len(stack) == 0