Valid Parentheses

Determine whether a parentheses string is well-formed

EasyStackString

Determine if the parentheses string is well-formed.

Examples

Example 1

Input: s = "()"
Output: true

Example 2

Input: s = "(]"
Output: false

Constraints

  • 1 ≤ |s| ≤ 10⁴

Tips

  • Push opening brackets onto a stack.
  • Pop only if the current closing bracket matches the stack top.

Hints

Show hint 1

Map each closing bracket to its matching opening bracket.

Show hint 2

Early exit when the stack is empty but a closing bracket appears.

Follow-up questions

What an interviewer might ask once you have a working solution.

  • How would you validate HTML/XML-like tags where tokens can be multi-character?
  • Can you extend this to handle wildcard characters such as '*'?

Practice this with an AI interviewer

Explain your approach out loud, write Python or JavaScript, run it against hidden tests (including large inputs), and get a scored debrief.

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