0921. Minimum Add to Make Parentheses Valid

# 921. Minimum Add to Make Parentheses Valid#

## 题目 #

Given a string S of ‘(’ and ‘)’ parentheses, we add the minimum number of parentheses ( ‘(’ or ‘)’, and in any positions ) so that the resulting parentheses string is valid.

Formally, a parentheses string is valid if and only if:

• It is the empty string, 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. Given a parentheses string, return the minimum number of parentheses we must add to make the resulting string valid.

Example 1:

``````
Input: "())"
Output: 1

``````

Example 2:

``````
Input: "((("
Output: 3

``````

Example 3:

``````
Input: "()"
Output: 0

``````

Example 4:

``````
Input: "()))(("
Output: 4

``````

Note:

1. S.length <= 1000
2. S only consists of ‘(’ and ‘)’ characters.

## 代码 #

``````
package leetcode

func minAddToMakeValid(S string) int {
if len(S) == 0 {
return 0
}
stack := make([]rune, 0)
for _, v := range S {
if v == '(' {
stack = append(stack, v)
} else if (v == ')') && len(stack) > 0 && stack[len(stack)-1] == '(' {
stack = stack[:len(stack)-1]
} else {
stack = append(stack, v)
}
}
return len(stack)
}

``````

Nov 25, 2022