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:
S.length <= 1000
S only consists of '(' and ')' characters.
class Solution:
    def minAddToMakeValid(self, S: str) -> int:
        res,need=0,0
        for i in range(len(S)):
            if S[i]=='(':
                need+=1
            if S[i]==')':
                need-=1
                if need==-1:
                    need=0
                    res+=1
        return res+need

class Solution:
    def minAddToMakeValid(self, S: str) -> int:
        res,need=0,0
        for i in range(len(S)):
            if S[i]=='(':
                need+=1
            if S[i]==')':
                need-=1
                if need==-1:
                    need=0
                    res+=1
        return res+need
