# LeetCodeAnimation > LeetCode solutions explained with animations: how pointers move, how states change, how recursion unfolds, and why boundary cases hold. > This GitHub copy is the public index and historical assets; **full step-through, replay, speed control, and voice walkthroughs live in the website version.** [![GitHub stars](https://img.shields.io/github/stars/MisterBooo/LeetCodeAnimation?style=social)](https://github.com/MisterBooo/LeetCodeAnimation) [![last commit](https://img.shields.io/github/last-commit/MisterBooo/LeetCodeAnimation?color=7c3aed)](https://github.com/MisterBooo/LeetCodeAnimation/commits/master) [![LeetCode animations](https://img.shields.io/badge/dynamic/json?url=https%3A%2F%2Fraw.githubusercontent.com%2FMisterBooo%2FLeetCodeAnimation%2Fmaster%2Fdocs%2Fdata%2Fstats.json&query=%24.count&label=LeetCode%20animations&color=7c3aed)](leetcode-animation-index.md) [![🎬 Interactive version](https://img.shields.io/badge/🎬_Interactive_version-step·speed·voice-7c3aed?style=for-the-badge)](https://www.algomooc.com/leetcode-animation?utm_source=github&utm_medium=readme&utm_campaign=lca_revamp&utm_content=hero_interactive_en) [![📚 Browse by topic](https://img.shields.io/badge/📚_Browse_by_topic-arrays·lists·DP·graphs…-1f6feb?style=for-the-badge)](https://www.algomooc.com/topics?utm_source=github&utm_medium=readme&utm_campaign=lca_revamp&utm_content=hero_topics_en) [![🤖 AI tutor Xiao Ou](https://img.shields.io/badge/🤖_AI_tutor-ask_anytime-16a34a?style=for-the-badge)](https://www.algomooc.com/ai-tutor?utm_source=github&utm_medium=readme&utm_campaign=lca_revamp&utm_content=hero_ai_xiaoou_en) If this project helps you, a **Star** keeps it visible and supports continued updates. --- ## 🚧 2026 Major Version In Progress This repo is not a one-off archive. A major 2026 upgrade is underway — **only shipped / in-progress facts are listed**: - ✅ **Three-language reference code**: every solution ships **Python / C++ / Java** implementations, Python by default. - ✅ **AI tutor "Xiao Ou"**: an AI algorithm tutor that answers follow-up questions on ideas and edge cases while you solve. - ✅ **Voice walkthroughs in Wu Shixiong's voice**: the animation narrates as it plays; the voice is **AI-synthesized (Wu Shixiong's voice, authorized)**. Hit 🔊 in the player. - 🚧 **Full quality pass over 299 problems**: a problem-by-problem quality review and remake, shipping in batches and synced back into this repo's index. > Progress flows into the "Current Index" below and [`sync-log.md`](sync-log.md) via the sync scripts. --- ## Website-Style Animation Previews These GIFs are captured from the website player. **Click any image to jump straight to its problem page** (full step playback, three-language code, and voice walkthrough are all in the website version).

Two Sum Scan the array while the hash table grows, then see exactly where the complement is found.	Trapping Rain Water Bar heights, boundaries, and trapped water are shown as separate moving states.
Number of Islands The DFS coloring process unfolds cell by cell, making connected components easier to inspect.	Linked List Cycle Slow and fast pointers move on the same list, so the meeting point becomes visible.

**↑ The website version also lets you step, replay, change speed, and listen** — [open the interactive version →](https://www.algomooc.com/leetcode-animation?utm_source=github&utm_medium=readme&utm_campaign=lca_revamp&utm_content=preview_cta_en) --- ## Highlights - **Animation-first**: understand the process first, then return to the code. Many problems keep GIFs or step-by-step animation assets. - **Three-language code**: each solution ships Python / C++ / Java reference implementations. - **Structured data**: [`data/manifest.json`](data/manifest.json) can be consumed by scripts for indexing, link checks, or downstream tooling. - **Continuous sync**: when the website adds or adjusts animations, scripts sync them back to GitHub — the repo is not a static archive. ## Current Index > The numbers below are injected by `tools/scripts/build-readme.js` from `docs/data/manifest.json`. **Do not edit by hand.** | Item | Count / Path | | :-- | :-- | | LeetCode animation items | **256** | | Easy | 71 | | Medium | 160 | | Hard | 25 | | Data file | [`data/manifest.json`](data/manifest.json) | | Index by number | [`leetcode-animation-index.md`](leetcode-animation-index.md) | | Index by topic | [`index-by-topic.md`](index-by-topic.md) | | Website path | | > **What the numbers mean**: **256** is the number of **LeetCode animations already synced into this repo** (computed by scripts from the website-side `study_index.js` → `manifest.json`). > The **299** mentioned above is **algomooc.com's full animation catalog** (including advanced problems and topic sets, from the site's `content-stats` single source) — a larger set than this repo's synced LeetCode subset. > Both numbers are **script-managed and never hand-typed**: 256 comes from this repo's manifest; 299 is backfilled from the site's content-stats (see the `siteTotal` field in [`data/stats.json`](data/stats.json)). --- ## Content Map | Goal | Start Here | | :-- | :-- | | Search animations by problem number | [`leetcode-animation-index.md`](leetcode-animation-index.md) | | Search animations by topic | [`index-by-topic.md`](index-by-topic.md) | | Process problem data with scripts | [`data/manifest.json`](data/manifest.json) | | Read earlier notes | [`notes/`](notes) or each problem's `Article/` folder under [`problems/`](../problems) | | Check earlier animation assets | Each problem's `Animation/` folder under [`problems/`](../problems) | | Read sync history | [`sync-log.md`](sync-log.md) | ---

🛠 Maintainers: sync & data notes (click to expand — readers can skip)

### Repository and website GitHub stores historical content, the public index, and sync scripts; the website maintains the current animation pages. Playback, step-through, and reading experience are authoritative on the website. The sync scripts write the website's problem list back into this repo for review, search, and versioning. ### Sync The website's problem index comes from `study_index.js`. Review first: ```bash npm run review:site ``` Once a sync is confirmed: ```bash npm run sync # update manifest / number index / topic index / sync log npm run validate # validate the manifest node tools/scripts/build-readme.js --write # re-inject README number blocks + stats.json ``` This updates: - `data/manifest.json` - `leetcode-animation-index.md` - `index-by-topic.md` - `sync-log.md` - `data/stats.json` and the `Current Index` marker blocks in both READMEs See [`sync-workflow.md`](sync-workflow.md) and [`HOW-TO-INTERACT.md`](HOW-TO-INTERACT.md) for the full workflow, commit rules, and number-ownership mechanism. ### Layout | Path | Notes | | :-- | :-- | | `data/manifest.json` | Structured LeetCode animation index (single source of truth for numbers) | | `data/stats.json` | Script-computed counts read by the README badge | | `leetcode-animation-index.md` | Markdown index generated from the manifest | | `index-by-topic.md` | Topic index generated from the manifest | | `sync-log.md` | Sync history | | `sync-workflow.md` | Website-to-GitHub workflow | | `../tools/scripts/review-site-changes.js` | Review whether website changes should be synced | | `../tools/scripts/sync-algomooc-index.js` | Sync script for the website-side index | | `../tools/scripts/validate-manifest.js` | Manifest validator | | `../tools/scripts/build-readme.js` | Inject README number blocks + generate `stats.json` | | `assets/previews/` | Website-style animation preview GIFs used by the READMEs | | `notes/` · `../problems/` | Historical notes, code, and animation assets |

--- ## ⭐ Star it to follow the updates [![Star History Chart](https://api.star-history.com/svg?repos=MisterBooo/LeetCodeAnimation&type=Date)](https://star-history.com/#MisterBooo/LeetCodeAnimation&Date) This project grew from hand-drawn animations to where it is today on the encouragement of every Star. If it helped you truly understand a problem, **a Star** is the most concrete support for continued updates. > 📌 Content is continuously synced from **[algomooc.com](https://www.algomooc.com/leetcode-animation?utm_source=github&utm_medium=readme&utm_campaign=lca_revamp&utm_content=footer_site_en)** — when the website updates, the repo index follows via scripts. ## 中文 See [`../README.md`](../README.md).