MinimumRemovetoMakeValidParentheses.py

"""
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:
        stack = []
        to_remove = set()

        for i, char in enumerate(s):
            if char == '(':
                stack.append(i)
            elif char == ')':
                if stack:
                    stack.pop()
                else:
                    to_remove.add(i)

        to_remove.update(stack)

        result = []
        for i, char in enumerate(s):
            if i not in to_remove:
                result.append(char)

        return ''.join(result)


if __name__ == "__main__":
    s = "lee(t(c)o)de)"
    solution = Solution()
    result = solution.minRemoveToMakeValid(s)
    print(result)  # Output: "lee(t(c)o)de"