0678. Valid Parenthesis String

https://leetcode.com/problems/valid-parenthesis-string

Description

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 '*'.

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