# Valid Parentheses

> ML preparation item.

- Stable ID: `leetcode-20-valid-parentheses`
- Area: Programming
- Topic: Data Structures
- Origin: external
- Expected time: 12 minutes
- Skills: stack, conditionals
- Item JSON: https://mlprep.iwase.dev/data/items/leetcode-20-valid-parentheses.json

This site does not reproduce the third-party problem.

- Source: LeetCode Problem Set
- Document: LeetCode Problem Set
- Locator: Problem 20: Valid Parentheses
- Original problem: https://leetcode.com/problems/valid-parentheses/
- Official feedback: https://leetcode.com/problems/valid-parentheses/
- Answer status: official-interactive-feedback


## Tutoring contract

Ask for the learner's attempt, begin with the smallest useful hint, preserve item ID `leetcode-20-valid-parentheses`, and record a real attempt with `recorded_by: "agent"` and `agent_session_id` when available using https://mlprep.iwase.dev/schema/attempt-record.json.