Valid Parentheses

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.
3. Every close bracket has a corresponding open bracket of the same type.

Example 1: Input: s = ”()” Output: true

Example 2: Input: s = ”()[]{}” Output: true

Example 3: Input: s = ”(]” Output: false

Example 4: Input: s = ”([])” Output: true

Example 5: Input: s = ”([)]” Output: false

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

My Answer

class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        parentheses = {'[':']', '(':')', '{':'}'}
        for item in s:
            if item in parentheses:
                stack.append(item)
            elif item in parentheses.values():
                if len(stack) == 0:
                    return False
                value=stack.pop()
                if parentheses[value] != item:
                    return False
        return stack == []

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