Leetcode Add To List

Add Problems to LeetCode List

Uses the LeetCode GraphQL API (addQuestionToFavorite mutation) via a browser session to bulk-add problems to a custom LeetCode problem list.

How LeetCode Lists Work

• Each custom list has a hash (e.g. dyf6r5b7) visible in its URL: https://leetcode.com/problem-list/<hash>/
• Problems are identified by their numeric ID (the number in the problem URL, e.g. 1 for Two Sum)
• The API uses the session cookies (especially csrftoken) from the logged-in browser — no separate auth needed

Prerequisites

• A browser session attached via playwright-cli CDP (usually port 9222)
• User must be logged into LeetCode in that browser
• The target problem list hash (from the URL)

Steps

1. Attach to the browser

playwright-cli attach --cdp=http://localhost:9222

2. Navigate to the target list page (establishes cookies)

playwright-cli goto https://leetcode.com/problem-list/<LIST_HASH>/

3. Add problems via GraphQL

Use playwright-cli run-code --filename=<script> with a script that calls page.evaluate:

async page => {
  const results = await page.evaluate(async () => {
    const problems = [
      {id: '1',   name: 'Two Sum'},
      {id: '217', name: 'Contains Duplicate'},
      // ... more problems
    ];

    const csrftoken = document.cookie.match(/csrftoken=([^;]+)/)?.[1] || '';
    const favoriteIdHash = 'dyf6r5b7'; // replace with actual list hash
    const results = [];
    const query = `mutation addQuestionToFavorite($favoriteIdHash: String!, $questionId: String!) {
      addQuestionToFavorite(favoriteIdHash: $favoriteIdHash, questionId: $questionId) {
        ok
        error
        questionId
        favoriteIdHash
      }
    }`;

    for (const p of problems) {
      const resp = await fetch('/graphql/', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'x-csrftoken': csrftoken,
          'Referer': `https://leetcode.com/problem-list/${favoriteIdHash}/`,
          'x-operation-name': 'addQuestionToFavorite',
        },
        body: JSON.stringify({
          operationName: 'addQuestionToFavorite',
          variables: { favoriteIdHash, questionId: p.id },
          query
        })
      });
      const data = await resp.json();
      results.push({
        name: p.name,
        id: p.id,
        ok: data?.data?.addQuestionToFavorite?.ok,
        error: data?.data?.addQuestionToFavorite?.error
      });
      await new Promise(r => setTimeout(r, 150)); // polite delay
    }
    return results;
  });
  return JSON.stringify(results, null, 2);
}

4. Verify

Reload the page and take a screenshot to confirm the question count.

AlgoMonster 50 Problem IDs

For the AlgoMonster Monster 50 list (read from https://algo.monster/practice/monster50):

Notes

• The mutation is idempotent — adding a problem that's already in the list returns ok: true without duplicating it
• questionId is a string, not an integer — pass the problem number as a string
• Graph Valid Tree (#261) is LeetCode Premium and may not appear in the public list count even though the API returns ok: true
• The browser automatically sends session cookies (auth) — no manual cookie handling needed
• The csrftoken cookie value must also be set as the x-csrftoken header — this is Django's double-submit CSRF protection (cookie alone isn't enough, header must match cookie)
• All fetch calls must be made via page.evaluate() so they run inside the browser context (same-origin, so cookies are sent automatically)