• 题目描述　　

 

　　　　

 

 

 

  • 题目分析
    • 其中 s.length < 25, 可以用枚举暴力来做
    • BFS一层一层枚举，这一层出现正确结果break
  • 　　 
     1 from collections import deque
 2 
 3 class Solution:
 4     def removeInvalidParentheses(self, s: str) -> List[str]:
 5 
 6         def check(s):
 7             cnt = 0
 8             for it in s:
 9                 if it == '(':
10                     cnt += 1
11                 elif it == ')':
12                     cnt -= 1
13                 if cnt < 0:
14                     return False
15             return cnt == 0
16 
17 
18         level = set([s])
19         while True:
20             ans = list(filter(check, level))
21             if ans: break
22 
23             states = set()
24             for s in level:
25                 for i, char in enumerate(s):
26                     if char in '()':
27                         state = s[:i] + s[i+1:]
28                         # print(state)
29                         if state not in states:
30                             states.add(state)
31             level = list(states)
32 
33         return ans