Valid Parenthesis String

MediumGreedygreedy

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

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Problem

You are given a string s containing only '(', ')' and '*'. Each '*' can independently stand for '(', ')', or nothing. Return true if some choice for the stars makes s a balanced parentheses string (every '(' has a matching later ')' and no prefix has more ')' than '('), and false otherwise. The empty string is balanced. Aim for O(n) time and O(1) space.

Examples

Input: s = "(*))"
Output: true
Treat the star as "(" to get "(())".
Input: s = "(()*("
Output: false
The final "(" has nothing after it to close it.

Constraints

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

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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