Minimum Remove To Make Valid Parentheses
Remove min parentheses to make valid string: remove unnecessary ( and ) while keeping valid chars. Two-pass approach: first pass removes invalid closing ), second pass removes invalid opening (.
1249. Minimum Remove to Make Valid Parentheses
Difficulty: Medium
Topics: String, Stack
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...