1249. Minimum Remove to Make Valid Parentheses

Medium

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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 with B), where A and B are valid strings, or

• It can be written as (A), where A 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 <= 105

• s[i] is either'(' , ')', or lowercase English letter.

class Solution:
    def minRemoveToMakeValid(self, s: str) -> str:
        left_index = []
        right_index = []
        for index, char in enumerate(list(s)):
            if char == "(":
                left_index.append(index)
            elif char == ")":
                if left_index and left_index[-1] < index:
                    left_index.pop()
                else:
                    right_index.append(index)
        array = list(s)
        left_index.extend(right_index)
        return "".join([char for idx, char in enumerate(array) if idx not in left_index])