README.md

---
license: cc-by-4.0
language:
  - en
pretty_name: LeetCode Problems Labelled by Solution Pattern (Sample)
size_categories:
  - n<1K
task_categories:
  - text-classification
tags:
  - code
  - algorithms
  - programming-problems
  - technical-interviews
  - leetcode
  - taxonomy
configs:
  - config_name: default
    data_files:
      - split: train
        path: data/train.jsonl
---

# LeetCode Problems Labelled by Solution Pattern (Sample)

A 100-problem sample of LeetCode problems annotated with the **algorithmic technique that solves
them**, rather than the topic tag that describes what they are about.

LeetCode's own tags answer "what is this problem about" — `Array`, `String`, `Hash Table`. That is
not the same question as "how is it solved". Both *Two Sum* and *Longest Substring Without Repeating
Characters* are tagged `Hash Table`, but one is a complement lookup and the other is a sliding window
with a seen-set. This dataset adds a `solution_archetype` field that answers the second question.

The full corpus this sample is drawn from covers 3,000 problems across 29 archetypes.

## Dataset structure

One JSON object per line in `data/train.jsonl`:

| field | type | description |
| --- | --- | --- |
| `problem_number` | int | The problem's number on LeetCode |
| `title` | string | Problem title |
| `slug` | string | URL slug |
| `difficulty` | string | `Easy`, `Medium` or `Hard` |
| `topic_tags` | list[string] | LeetCode's own topic tags, unmodified |
| `solution_archetype` | string | **The annotation.** The technique that solves the problem |
| `has_reference_solution` | bool | Whether a worked reference solution exists for this problem |
| `leetcode_url` | string | Canonical problem URL on leetcode.com |
| `pattern_reference` | string \| null | Write-up of the archetype, where one exists |

### Sample row

```json
{
  "problem_number": 1,
  "title": "Two Sum",
  "slug": "two-sum",
  "difficulty": "Easy",
  "topic_tags": ["Array", "Hash Table"],
  "solution_archetype": "hash-map",
  "has_reference_solution": true,
  "leetcode_url": "https://leetcode.com/problems/two-sum/",
  "pattern_reference": "https://www.stealthinterview.ai/leetcode/patterns/hash-map"
}
```

### Composition of this sample

100 problems, stratified to cover as many archetypes as possible while keeping the difficulty mix of
the source corpus: **21 Easy / 63 Medium / 16 Hard**, spanning **29 distinct archetypes**. Selection
is deterministic — problems are taken in ascending number, round-robin across archetypes — so the
sample is reproducible rather than a random draw. Premium-only problems are excluded, because their
statements are not publicly checkable.

## Usage

```python
from datasets import load_dataset

ds = load_dataset("<your-username>/leetcode-solution-patterns-sample", split="train")

# Problems solved by a monotonic stack
mono = ds.filter(lambda r: r["solution_archetype"] == "monotonic-stack")

# Where LeetCode's tag and the solving technique disagree
mismatch = ds.filter(
    lambda r: "Hash Table" in r["topic_tags"] and r["solution_archetype"] != "hash-map"
)
```

## Provenance and what is actually original here

This distinction matters, so it is stated plainly:

- **Not original, and not owned by this dataset:** problem numbers, titles, slugs, difficulty ratings
  and topic tags. These are factual references to problems hosted on LeetCode.
- **Original:** the `solution_archetype` labels and the taxonomy of 29 archetypes they are drawn
  from. These were derived by analysing solution structure across the corpus and are the reason this
  dataset exists.

**No problem statements, test cases, editorial content or LeetCode solutions are included in this
dataset.** Only metadata and links back to the canonical problem pages. If you need the problem text,
follow `leetcode_url`.

LeetCode is a trademark of its respective owner. This dataset is not affiliated with, endorsed by, or
sponsored by LeetCode.

## Licence

The **annotations** — `solution_archetype` and the taxonomy — are released under
[CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). Attribution is appreciated if you use the
labels in research or a downstream dataset.

The referenced problem metadata is factual information about a third-party platform and is not
claimed under this licence.

## Limitations

- **One archetype per problem.** Many problems admit more than one valid approach; the label records
  the technique the reference solution used, not the only one that works.
- **`bespoke` is a real category, not a fallback for hard problems.** It marks problems whose
  solution does not generalise to a reusable pattern.
- **The taxonomy is opinionated.** Where you draw the line between `stack` and `monotonic-stack`, or
  `dfs` and `graph-traversal`, is a judgement call. The boundaries here are consistent within the
  corpus but are not a standard anyone else has ratified.
- **Sample, not corpus.** 100 of 3,000. Frequencies here will not match the full distribution.

## Source

Built from the problem library at
[stealthinterview.ai/leetcode](https://www.stealthinterview.ai/leetcode), which organises the full
3,000-problem set by solving technique. The archetype taxonomy and the per-technique write-ups —
including the template, complexity and applicable problems for each — are documented at
[stealthinterview.ai/leetcode/patterns](https://www.stealthinterview.ai/leetcode/patterns).

## Citation

```bibtex
@misc{leetcode_solution_patterns_2026,
  title  = {LeetCode Problems Labelled by Solution Pattern},
  year   = {2026},
  url    = {https://www.stealthinterview.ai/leetcode/patterns},
  note   = {Sample of 100 problems annotated with solving technique}
}
```