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.
Solution
关于括号匹配，很自然想起用stack来求解
class Solution(object):
def isValid(self, s):
"""
:type s: str
:rtype: bool
"""
amap = {")": "(", "]": "[", "}": "{"}
astack = []
for i in s:
if i not in amap:
astack.append(i)
else:
if not astack or astack.pop() != amap.get(i):
return False
return not astack
