題目描述：

示例：

知識點：

一：一連串的判斷

 7 class Solution:
 8     def isValid(self, s: str) -> bool:
 9         temp = []
10 
11         for item in s:
12             if item in ['(', '{', '[']:
13                 temp.append(item)
14             else:
15                 if len(temp) != 0:
16                     c = temp.pop()
 
17                     if c == '(' and item != ')':
18                         return False
19                     if c == '[' and item != ']':
20                         return False
21                     if c == '{' and item != '}':
22                         return False
23                 else:
 
24                     return False
25         if len(temp) != 0:
26             return False
27         else:
28             return True

二：字典的使用

 1 class Solution:
 2     def isValid(self, s: str) -> bool:
 3         dic = {'(':')', '{':'}', '[':']'}
 4         sta = []
 5         for c in s:
 
 6             if c in ['(', '[', '{']:
 7                 sta.append(c)
 8             elif sta:
 9                 if c != dic[sta.pop()]:
10                     return False
11             else:
12                 return False
13         return True if len(sta) == 0 else False

四：字串的妙用

1 class Solution:
2     def isValid(self, s: str) -> bool:
3         while '()' in s or '[]' in s or '{}' in s:
4             s=s.replace('()', '').replace('[]', '').replace('{}', '')
5         return True if len(s) == 0 else False

三：衛兵的使用

 1 class Solution:
 2     def isValid(self, s: str) -> bool:
 3         dic = {'(':')', '{':'}', '[':']', '?':'?'}
 4         sta = ['?']
 5         for c in s:
 6             if c in ['(', '[', '{']:
 7                 sta.append(c)
 8             elif c != dic[sta.pop()]:
 9                 return False
10         return True if len(sta) == 1 else False