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)"

Constraints:

· 1 <= s.length <= 10^5

· s[i] is one of  '(' , ')' and lowercase English letters.

Solution:

``````
func minRemoveToMakeValid(s string) string {
stack := []int{}
lenS := len(s)
remove := []int{}

for i:= 0; i < lenS; i++ {
switch s[i] {
case '(':
stack = append(stack, i)

case ')':
if len(stack) == 0 {
remove = append(remove, i)
} else {
stack = stack[:len(stack) - 1]
}
}
}
var ns strings.Builder
for i:= 0; i < lenS; i++ {
switch {
case (len(remove) > 0) && (remove[0] == i):
remove = remove[1:]
continue
case  (len(stack) > 0) && (stack[0] == i):
stack = stack[1:]
continue
}

ns.WriteByte(s[i])
}
return ns.String()
}

``````