Valid Parentheses

From LeetCode

problem description / solution

Solution in Python3

class Solution:
    def isValid(self, s: str) -> bool:
        pairs = {
            '(': ')',
            '{': '}', 
            '[': ']'
        }

        stack = []
        for c in s:
            if c in pairs:
                stack.append(c)
            elif not stack or pairs[stack.pop()] != c:
                return False
        return not stack

I am lucky to get

Runtime: 36 ms, faster than 86.12% of Python3 online submissions for Valid Parentheses.

Time Complexity

\(O(l)\), where \(l\) is the length of s.