Minimum Remove to Make Valid Parentheses

Question

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.

Accepted Answer

A detailed reference solution is available to Crack ML Interview members.