Minimum_Add_To_Make_Parentheses Valid.cpp

PROBLEM STATEMENT :- 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
  
  SOLUTION :-
    class Solution {
public:
    int minAddToMakeValid(string s) 
    {
        stack<char> st;
        for(int i=0;i<s.size();i++)
        {
            if(s[i]=='(')
            {
                st.push('(');
            }
            else 
            {
                if(st.empty()==false && st.top() == '(')
                    st.pop();
                else
                    st.push(s[i]);
            }
        }
        return st.size();
    }
};