Validate SleightOfHand input

[krotname]

Motivation

• Prevent crashes and denial-of-service from untrusted stdin by bounding token reads and validating grid cell values before using them as array indexes.

Description

• Add a bounded token reader next(int maxLength) and switch board reads to in.next(4) so oversized row tokens are rejected before unbounded buffer growth can exhaust memory.
• Validate each CLI grid character and throw an IOException for any non-. and non-digit character before indexing count[ch - '0'].
• Wrap main invocation in a try/catch to report IOException and IllegalArgumentException messages instead of letting uncaught exceptions crash the process.
• Validate caller-supplied matrix values in solve(int, int[][]) and throw IllegalArgumentException for values outside 0..9 before indexing the digit count array.

Testing

• mvn test -q was attempted but failed due to Maven Central returning 503 Service Unavailable while resolving the JUnit BOM.
• Compiled the class with javac and ran a valid sample input which produced the expected output 2 (succeeded).
• Ran a malformed grid containing ! and observed a handled IOException with message Invalid grid cell: ! (succeeded).
• Ran a very large token under -Xmx16m and observed IOException: Token length exceeds 4, preventing heap exhaustion (succeeded).
• Executed a small harness calling solve(1, new int[][]{{10,0,0,0}}) and observed IllegalArgumentException: Grid values must be between 0 and 9 (succeeded).

---

Codex Task

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: d1e321ac30

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[sonarqubecloud]

Quality Gate failed

Failed conditions
52.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 23.07692% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...rc/main/java/algorithms/sprint1/SleightOfHand.java	23.07%	8 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!

[krotname]

Закрываю как superseded by #116: изменения перенесены в одну проверенную ветку, все review findings учтены; локальный mvn verify прошёл полностью.