Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add Arcadi4/nerdy --skill elementary-data-structuresgit clone --depth 1 https://github.com/Arcadi4/nerdyWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/arcadi4/nerdy/elementary-data-structures)<a href="https://agentmods.dev/skills/arcadi4/nerdy/elementary-data-structures"><img src="https://agentmods.dev/badge/skills/arcadi4/nerdy/elementary-data-structures/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/arcadi4/nerdy/elementary-data-structures"><img src="https://agentmods.dev/badge/skills/arcadi4/nerdy/elementary-data-structures.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00053 | $0.02890 |
| Opus 5.5 | $0.00021 | $0.01156 |
| Sonnet 5.5 | $0.00011 | $0.00578 |
| Haiku 4.5 | $0.00005 | $0.00289 |
Grade A, and why
elementary-data-structures scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 193 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Elementary Data Structures
Overview
Treat elementary data structures as representation contracts, not classroom containers. The core move is to name the operations, access pattern, ownership model, and boundary invariants before choosing arrays, lists, stacks, queues, or tree links.
Shared CLRS Conventions
Follow the parent clrs skill for mathematical formatting, formula-free headings, direct polished answers, and CLRS-wide answer style.
When to Use
- A problem asks for arrays, matrices, stacks, queues, linked lists, sentinels, rooted trees, or left-child/right-sibling representation.
- You need to implement or review a dynamic set with
SEARCH,INSERT,DELETE,MINIMUM,MAXIMUM,SUCCESSOR, orPREDECESSOR-like operations. - A design hinges on contiguity, locality, pointer chasing, deletion by pointer, circular-buffer wraparound, sentinel nodes, or parent/child/sibling navigation.
- A production discussion needs the lesson behind an undergraduate structure rather than a literal reimplementation.
Do not use this skill merely because code contains an array or list. Use ordinary language/library conventions unless representation choice, invariants, asymptotic behavior, or access patterns are central.
First Decision: What Contract Does the Structure Serve?
| Need | Prefer | Why |
|---|---|---|
| Random indexed access and dense storage | Contiguous array or vector | Index arithmetic is constant time and cache-friendly |
| Append/pop at one end | Dynamic array or stack abstraction | Simpler and more local than pointer nodes |
| FIFO bounded buffer | Circular array queue | Constant-time operations with fixed memory and explicit full/empty policy |
| Frequent middle splice with existing node handles | Doubly linked list | Pointer rewiring is constant time once the node is known |
| Search by key in an unordered small set | Array or list if tiny; otherwise a real dictionary | Elementary structures expose the cost; later chapters provide better dictionaries |
| Ordered enumeration from elementary structures only | Sorted array/list if updates are rare | Maintaining order shifts update cost somewhere |
| Variable-arity rooted tree | Child vectors or left-child/right-sibling | Choose by child iteration, random child access, memory, and parent navigation |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 193 lines · 53 tokens per session scan A c2129b9583d9
elementary-data-structures is a skill published in the GitHub repository Arcadi4/nerdy (6 stars, last pushed 6mo ago), licensed MIT. It adds 53 tokens to every session and 2,890 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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