Valid Parenthesis String

 

 Valid Parenthesis String

Given a string containing only three types of characters: '(', ')' and '*', write a function to check whether this string is valid. We define the validity of a string by these rules:

1. Any left parenthesis '(' must have a corresponding right parenthesis ')'.
2. Any right parenthesis ')' must have a corresponding left parenthesis '('.
3. Left parenthesis '(' must go before the corresponding right parenthesis ')'.
4. '*' could be treated as a single right parenthesis ')' or a single left parenthesis '(' or an empty string.
5. An empty string is also valid.

 

Example 1:

Input: "()"
Output: True

Example 2:

Input: "(*)"
Output: True

Example 3:

Input: "(*))"
Output: True

Note:

1. The string size will be in the range [1, 100].

class Solution {
public:
    bool checkValidString(string s)
    {
        stack<int> open,star;
        int i=0;
        if(s.size()==1&&s[0]==')')
            return false;
           
        while(i<s.size())
        {
   
            if(s[i]=='(')
            {
                open.push(i);
            }
            else if(s[i]==')')
            {
                 if(!open.empty())
                      open.pop();
                  else if(!star.empty())
                      star.pop();
                   else
                       return false;
            }
            else if(s[i]=='*')
              {
               star.push(i);
            }
            ++i;
        }
        while(open.size()>0)
        {
            if(star.empty())return false;
            if(open.top()<star.top())
            {
                open.pop(),star.pop();
               
            }else{
                return false;
            }
        }
       
            return true;
        
     
    }
};