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ValidParenthesis.py
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ValidParenthesis.py
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# 20. Valid Parentheses
# Easy
# Given a string 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.
# Note that an empty string is also considered valid.
# Example 1:
# Input: "()"
# Output: true
# Example 2:
# Input: "()[]{}"
# Output: true
# Example 3:
# Input: "(]"
# Output: false
# Example 4:
# Input: "([)]"
# Output: false
# Example 5:
# Input: "{[]}"
# Output: true
# My Solution
class Solution:
def isValid(self, s: str) -> bool:
k = {")": "(", "]": "[", "}":"{"}
stack = []
for c in s:
if c in k:
top = stack.pop() if len(stack) > 0 else "x"
if k[c] != top: return False
else:
stack.append(c)
return len(stack) == 0