class Solution(object):
def isValid(self, s):
"""
:type s: str
:rtype: bool
"""
"""
Time Complexity: O(n^2) because str.replace: O(n)
也可以利用老方法 stack
"""
while '()' in s or '{}' in s or '[]' in s:
s = s.replace('{}','').replace('()','').replace('[]','')
return s == '':
