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:
Any left parenthesis '(' must have a corresponding right parenthesis ')'.
Any right parenthesis ')' must have a corresponding left parenthesis '('.
Left parenthesis '(' must go before the corresponding right parenthesis ')'.
'*' could be treated as a single right parenthesis ')' or a single left parenthesis '(' or an empty string.
An empty string is also valid.
Example 1:
Input: "()"
Output: True
Example 2:
Input: "(*)"
Output: True
Example 3:
Input: "(*))"
Output: True
Note:
The string size will be in the range [1, 100].
class Solution:
     def checkValidString(self, s):
         """
         :type s: str
         :rtype: bool
         """
         l = r = star = 0
         
         for c in s:
             if c == "(":
                 l+=1
             if c == ")":
                 r+=1
             if c == "*":
                 star+=1
             if r > star + l:
                 return False
             
         l = r = star = 0
         
         for c in s[::-1]:
             if c == "(":
                 l +=1
             if c == ")":
                 r +=1
             if c == "*":
                 star +=1
             if l > star + r:
                 return False
         return True
class Solution:
     def checkValidString(self, s):
         """
         :type s: str
         :rtype: bool
         """
         l = r = star = 0
         
         for c in s:
             if c == "(":
                 l+=1
             if c == ")":
                 r+=1
             if c == "*":
                 star+=1
             if r > star + l:
                 return False
             
         l = r = star = 0
         
         for c in s[::-1]:
             if c == "(":
                 l +=1
             if c == ")":
                 r +=1
             if c == "*":
                 star +=1
             if l > star + r:
                 return False
         return True