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valid_parentheses.py
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valid_parentheses.py
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#!/usr/bin/env python
# encoding: utf8
# 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.
__author__ = "Zhu Xianfeng <[email protected]>"
class Solution:
# @return a boolean
def isValid(self, s):
stack = []
for c in s:
if c in ('(', '{', '['):
stack.append(c)
elif c in (')', '}', ']'):
if len(stack) < 1:
return False
left = stack.pop()
if (left, c) not in (('(', ')'), ('{', '}'), ('[', ']')):
return False
else:
return False
if len(stack) != 0:
return False
return True
def main():
s = "({[]})"
sol = Solution()
print sol.isValid(s)
if __name__ == "__main__":
main()