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921. Minimum Add to Make Parentheses Valid (Medium)

A parentheses string is valid if and only if:

• It is the empty string,
• 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.

You are given a parentheses string s. In one move, you can insert a parenthesis at any position of the string.

• For example, if s = "()))", you can insert an opening parenthesis to be "(()))" or a closing parenthesis to be "())))".

Return the minimum number of moves required to make s valid.

 

Example 1:

Input: s = "())"
Output: 1

Example 2:

Input: s = "((("
Output: 3

Example 3:

Input: s = "()"
Output: 0

Example 4:

Input: s = "()))(("
Output: 4

 

Constraints:

• 1 <= s.length <= 1000
• s[i] is either '(' or ')'.

Related Topics

[String] [Stack] [Greedy]

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