valid_parenthesis_string.py

"""
Given a string s containing only three types of characters: '(', ')' and '*', return true if s is valid.

The following rules define a valid string:

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 "".
 

Example 1:

Input: s = "()"
Output: true
Example 2:

Input: s = "(*)"
Output: true
Example 3:

Input: s = "(*))"
Output: true
 

Constraints:

1 <= s.length <= 100
s[i] is '(', ')' or '*'.

"""

class Solution:
    def checkValidString(self, s: str) -> bool:
        leftMin = 0
        leftMax = 0
        for i in s:
            if i == "(":
                leftMin = leftMin + 1
                leftMax = leftMax + 1
            elif i == ")":
                leftMin = leftMin - 1
                leftMax = leftMax - 1
            else:
                leftMin = leftMin - 1
                leftMax = leftMax + 1
            if leftMax < 0:
                return False
            if leftMin < 0:
                leftMin = 0
        if leftMin == 0:
            return True
        return False