678. Valid Parenthesis String LeetCode Solution | Easy Approach

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Valid Parenthesis String 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


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

Valid Parenthesis String Solutions

Time: O(n)
Space: O(n)


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