1249. Minimum Remove to Make Valid Parent
set string
Given a string s of '('
, ')'
and lowercase English characters.
Your task is to remove the minimum number of parentheses ( '('
or ')'
, in any positions ) so that the resulting parentheses string is valid and return any valid string.
Formally, a parentheses string is valid if and only if:
It is the empty string, contains only lowercase characters, or
It can be written as
AB
(A
concatenated withB
), whereA
andB
are valid strings, orIt can be written as
(A)
, whereA
is a valid string.
Example 1:
Input: s = "lee(t(c)o)de)"
Output: "lee(t(c)o)de"
Explanation: "lee(t(co)de)" , "lee(t(c)ode)" would also be accepted.
Example 2:
Input: s = "a)b(c)d"
Output: "ab(c)d"
Example 3:
Input: s = "))(("
Output: ""
Explanation: An empty string is also valid.
Constraints:
1 <= s.length <= 10
5
s[i]
is either'('
,')'
, or lowercase English letter.
分析:只存index。stack存(, to_remove存)用栈得到需要去掉的所有index,然后从s里去除掉这些Index
from collections import deque
class Solution:
def minRemoveToMakeValid(self, s: str) -> str:
stack = []
to_remove = set()
for i,c in enumerate(s):
if c == '(':
stack.append(i)
elif c == ')':
if stack:
stack.pop()
else:
to_remove.add(i)
to_remove.update(stack)
return ''.join(c for i,c in enumerate(s) if i not in to_remove)
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