algorithms/stack/valid_parenthesis.py at master · BeFreeB/algorithms · GitHub

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"""

Given a string containing just the characters

'(', ')', '{', '}', '[' and ']',

determine if the input string is valid.

The brackets must close in the correct order,

"()" and "()[]{}" are all valid but "(]" and "([)]" are not.

"""

def is_valid(s:"str")->"bool":

stack = []

dic = { ")":"(",

"}":"{",

"]":"["}

for char in s:

if char in dic.values():

stack.append(char)

elif char in dic.keys():

if stack == []:

return False

s = stack.pop()

if dic[char] != s:

return False

return stack == []

if __name__ == "__main__":

paren = "[]"

print(paren, is_valid(paren))

paren = "[]()[]"

print(paren, is_valid(paren))

paren = "[[[]]"

print(paren, is_valid(paren))

paren = "{([])}"

print(paren, is_valid(paren))

paren = "(}"

print(paren, is_valid(paren))

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