Valid Parentheses - Leetcode 20 - Python Stack

Valid Parentheses

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

An input string is valid if:

Open brackets must be closed by the same type of brackets.

Open brackets must be closed in the correct order.

class Solution:

def isValid(self, s: str) -> bool:

stack = []

hm = {

")" : "(",

"]" : "[",

"}" : "{"

}

for p in s:

if p in hm :

if stack and stack[-1] == hm[p]:

stack.pop()

else :

return False

else :

stack.append(p)

return True if not stack else False

Explaination :

Comments

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