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 sequenzia/agent-alchemy --skill string-algorithmsgit clone --depth 1 https://github.com/sequenzia/agent-alchemyWrote 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/sequenzia/agent-alchemy/string-algorithms)<a href="https://agentmods.dev/skills/sequenzia/agent-alchemy/string-algorithms"><img src="https://agentmods.dev/badge/skills/sequenzia/agent-alchemy/string-algorithms/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/sequenzia/agent-alchemy/string-algorithms"><img src="https://agentmods.dev/badge/skills/sequenzia/agent-alchemy/string-algorithms.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 | $0.00059 | $0.04391 |
| Opus 5.5 | $0.00024 | $0.01756 |
| Sonnet 5.5 | $0.00012 | $0.00878 |
| Haiku 4.5 | $0.00006 | $0.00439 |
Grade A, and why
string-algorithms 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 — 451 lines — stays where its author put it; the contents beside it link to each section on GitHub.
String Algorithm Patterns
This reference covers seven foundational string algorithms used in competitive programming and technical interviews. Each pattern includes recognition signals, a core idea explanation, a Python template, and notes on edge cases and common mistakes. Use the pattern recognition table to match problem constraints to the right technique, then drill into the individual pattern section.
Pattern Recognition Table
| Trigger Signals | Technique | Typical Complexity |
|---|---|---|
| Find pattern in text, exact match, prefix function | KMP | O(N + M) |
| Longest common prefix at each position, string period | Z-function | O(N) |
| Multiple pattern search, rolling hash, substring fingerprint | Rabin-Karp | O(N + M) average |
| Longest palindromic substring, count palindromes | Manacher's | O(N) |
| Fast substring comparison, equality checks in O(1) | String Hashing | O(N) preprocess, O(1) query |
| Lexicographic ordering of suffixes, LCP queries, substring counting | Suffix Array | O(N log N) build |
| Dictionary of patterns matched against text, multi-pattern search | Aho-Corasick | O(N + M + Z) |
Where N = text length, M = pattern length (or total pattern lengths), Z = number of matches.
Constraint-to-Technique Mapping
- Single pattern, exact match, N up to 10^6: KMP or Z-function
- All prefix-suffix overlaps: KMP failure function gives overlap chain
- String periodicity or repetition: Z-function (period = smallest i where z[i] + i == N)
- Multiple patterns, moderate count (< 100): Rabin-Karp with rolling hash
- Multiple patterns, large dictionary (10^3+): Aho-Corasick automaton
- Palindrome queries: Manacher's for longest; hashing + binary search for arbitrary checks
- Substring equality or comparison in O(1): Polynomial string hashing with double hash
- Lexicographic queries, distinct substrings, LCP: Suffix array + LCP array
KMP (Knuth-Morris-Pratt)
Recognition Signals
- Find all occurrences of a pattern in a text
- Compute the longest proper prefix that is also a suffix (failure/border array)
- Pattern matching without backtracking on the text pointer
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 · 451 lines · 59 tokens per session scan A bd7c0580a800
string-algorithms is a skill published in the GitHub repository sequenzia/agent-alchemy (45 stars, last pushed 4mo ago), licensed MIT. It adds 59 tokens to every session and 4,391 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 2026-08-30.
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