Solution
from typing import List
class Solution:
def removeInvalidParentheses(self, s: str) -> List[str]:
def dfs(i, l, r, lcnt, rcnt, t):
if i == n:
if l == 0 and r == 0:
ans.add(t)
return
if n - i < l + r or lcnt < rcnt:
return
if s[i] == '(' and l:
dfs(i + 1, l - 1, r, lcnt, rcnt, t)
elif s[i] == ')' and r:
dfs(i + 1, l, r - 1, lcnt, rcnt, t)
dfs(i + 1, l, r, lcnt + (s[i] == '('), rcnt + (s[i] == ')'), t + s[i])
l = r = 0
for c in s:
if c == '(':
l += 1
elif c == ')':
if l:
l -= 1
else:
r += 1
ans = set()
n = len(s)
dfs(0, l, r, 0, 0, '')
return list(ans)
if __name__ == "__main__":
sol = Solution()
print(sol.removeInvalidParentheses("()())()"))
# ['(())()', '()()()']
print(sol.removeInvalidParentheses("(a)())()"))
# ["(a())()","(a)()()"]
print(sol.removeInvalidParentheses(")("))
# [""]