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 Bare 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.

使用栈。

Runtime: 0 ms, faster than 100.00% of C++ online submissions forMinimum Add to Make Parentheses Valid.

#include
     
      #include
      
       #include 
       
        using namespace std;class Solution {public:    int minAddToMakeValid(string S) {        stack
        
          st;        for(auto a: S){            if('('==a)                st.push(a);            else if(!st.empty()&&st.top()=='('){                st.pop();            }else{                st.push(a);            }        }        return st.size();    }};int main(){    Solution solution=Solution();    cout<
         
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