# 1249. Minimum Remove to Make Valid Parentheses

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.

Example 4:

Input: s = "(a(b(c)d)"
Output: "a(b(c)d)"

# Solution

Approach 1: stack.

# Code (Python)

Approach 1:

class Solution:
    def minRemoveToMakeValid(self, s: str) -> str:
        stack = []
        for i in range(len(s)):
            if s[i] not in ('(', ')'):
            if s[i] == '(':
                if stack and s[stack[-1]] == '(':
        stack = set(stack)
        result = []
        for i in range(len(s)):
            if i in stack:
        return ''.join(result)

# Code (C++)

Approach 1:

Approach 2: