Add GPT-5-mini auto-solver for daily LeetCode problems

[Copilot]

Implements automated solution generation for daily LeetCode problems using OpenAI's GPT-5-mini, running at 00:01 UTC.

Changes

• .github/workflows/auto_solver.yml: Daily workflow with explicit contents: write permissions
• auto_solver.py: Fetches problem via LeetCode GraphQL API, generates solution with GPT-5-mini, saves as problems/{ID}/gpt5-mini.md
• README.md: Added auto-solver documentation

Generated Solution Format

Solutions follow existing template structure:

# [Problem {ID}: {Title}]({Link})

## Initial thoughts (stream-of-consciousness)
[AI analysis]

## Refining the problem, round 2 thoughts
[Complexity considerations]

## Attempted solution(s)
[Python solution with implementation notes]

Configuration Required

Set OPENAI_API_KEY repository secret before merge. Workflow can also be triggered manually via Actions UI.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• leetcode.com
  • Triggering command: `python3 -c
    import requests
    import json

Test fetching the daily problem

leetcode_api_url = 'REDACTED'
daily_challenge_query = {
'query': '''query questionOfToday {
activeDailyCodingChallengeQuestion {
date
link
question {
questionFrontendId
title
titleSlug
difficulty
content
}
}
}''',
'operationName': 'questionOfToday'
}

response = requests.post(leetcode_api_url, json=daily_challenge_query)
data = response.json()

if 'data' in data and 'activeDailyCodingChallengeQuestion' in data['data']:
question = data['data']['activeDailyCodingChallengeQuestion']['question']
print(f'✓ Successfully fetched daily problem:')
print(f' Problem ID: {question["questionFrontendId"]}')
print(f' Title: {question["title"]}')
print(f' Difficulty: {question["difficulty"]}')
print(f' Content length: {len(question["content"])} characters')
else:
print('✗ Failed to fetch problem')
print(json.dumps(data, indent=2))` (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>auto-solver?</issue_title>
<issue_description>It could be interesting to add in an "automatic solver" for each day's problem. E.g., could we construct an action to do the following (run each day at 0:01 UTC):

• fetch the daily problem
• store the text of the problem in a "problems" directory
• use langchain/chatgpt to solve the problem, describing the thought process and code using the attached template
• add chatgpt's solution under problems//chatgpt.md
• commit the notes/solution</issue_description>

Comments on the Issue (you are @copilot in this section)

@jeremymanning Updates: - Use GPT-5 mini to create each day's solution (API key is stored as a repo secret: OPENAI_API_KEY)

• Fixes auto-solver? #39

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[jeremymanning]

@copilot Since we can't test the key elements of this implementation here (i.e., fetching the leetcode problem doesn't work because we don't have access to external sites, and we can't access repository secrets to get the openai API key), add a comment ot the pull request with instructions for manually testing the solution before I merge.

[Copilot]

@copilot Since we can't test the key elements of this implementation here (i.e., fetching the leetcode problem doesn't work because we don't have access to external sites, and we can't access reposito...

Manual Testing Instructions

Since this PR cannot be fully tested in the PR environment, follow these steps to test before merging:

Prerequisites

1. Ensure OPENAI_API_KEY repository secret is set with a valid GPT-5-mini API key
2. Have access to the repository's Actions tab

Testing Steps

1. Manual Workflow Trigger Test

1. Go to Actions → "Auto-solve Daily LeetCode Problem"
2. Click "Run workflow" → Select main branch → Click "Run workflow"
3. Monitor the workflow execution:
   • ✓ Check that Python 3.11 installs successfully
   • ✓ Check that requests and openai packages install
   • ✓ Verify script fetches today's problem (look for problem ID/title in logs)
   • ✓ Confirm GPT-5-mini generates a solution (watch for "Solution generated successfully!")
   • ✓ Verify file is saved to problems/{PROBLEM_ID}/gpt5-mini.md
   • ✓ Confirm auto-commit pushes the new file

2. Verify Generated Solution

1. Navigate to problems/{PROBLEM_ID}/ (use today's problem ID from logs)
2. Open gpt5-mini.md and verify it contains:
   • Problem title and link
   • "Initial thoughts" section with analysis
   • "Refining the problem" section with complexity notes
   • Python solution in code block
   • Implementation notes

3. Validate Solution Quality

• Check that the Python code is syntactically valid
• Verify the solution approach makes sense for the problem
• Confirm complexity analysis is included

4. Test Schedule (Optional)

• Wait until 00:01 UTC tomorrow to verify automatic execution
• Check that workflow runs without manual trigger
• Verify new solution file appears automatically

Expected Output Structure

problems/
  └── {PROBLEM_ID}/
      └── gpt5-mini.md  ← Should be created with full solution

Troubleshooting

• Workflow fails at "Run auto-solver": Check OPENAI_API_KEY secret is set correctly
• "Failed to fetch daily problem": LeetCode API might be temporarily down (retry)
• "Failed to generate solution": Verify GPT-5-mini model access with your API key
• No commit pushed: Check workflow logs for file creation errors

[jeremymanning]

lgtm!