LintCode:有效的括号序列

( or { or [

class Solution:
# @param {string} s A string
# @return {boolean} whether the string is a valid parentheses
def isValidParentheses(self, s):
# Write your code here
if len(s) % 2 == 1 or len(s) == 0:
return False
L1 = []
for ch in s:
if ch == '{' or ch == '(' or ch == '[':
L1.append(ch)
else:
if ch == '}':
if L1:
if L1.pop() == '{':
pass
else:
return False
else:
return False
if ch == ']':
if L1:
if L1.pop() == '[':
pass
else:
return False
else:
return False
if ch == ')':
if L1:
if L1.pop() == '(':
pass
else:
return False
else:
return False
if L1:
return False
return True