feat(arrays, puzzles, matrix): lucky number in a matrix

[BrianLusina]

Describe your change:

Finds the lucky number in a matrix where a lucky number is a number that is the minimum in its row, but the maximum in its column

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

Summary by CodeRabbit

• New Features

  • Added a new array puzzle: "Lucky Numbers In A Matrix" with two solution variants.

• Documentation

  • Added a comprehensive README for the puzzle: description, constraints, visual examples, algorithm steps, and complexity analysis.

• Tests

  • Added thorough unit tests covering multiple scenarios and edge cases for both solution variants.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Adds a new "Lucky Numbers in a Matrix" puzzle: documentation, two implementations (lucky_numbers, lucky_numbers_simulation), and parameterized unit tests; also registers the puzzle in DIRECTORY.md.

Changes

Cohort / File(s)	Summary
Directory Index DIRECTORY.md	Inserts a new entry linking the "Lucky Numbers In A Matrix" puzzle and its test.
Documentation puzzles/arrays/lucky_numbers_in_a_matrix/README.md	Adds full README: problem statement, constraints, examples, greedy approach explanation, stepwise algorithm, and complexity analysis.
Implementation puzzles/arrays/lucky_numbers_in_a_matrix/__init__.py	Adds lucky_numbers(matrix: List[List[int]]) -> List[int] and lucky_numbers_simulation(matrix: List[List[int]]) -> List[int] with type hints, docstrings, and complexity notes.
Tests puzzles/arrays/lucky_numbers_in_a_matrix/test_lucky_numbers_in_a_matrix.py	New parameterized test module validating both functions across multiple matrices and edge cases.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20–30 minutes

• Verify correctness of both implementations (the single-result greedy variant vs. the simulation collection).
• Check handling of edge cases: empty matrix, single-row/column, rectangular shapes, and no-lucky-number cases.
• Review tests for sufficient coverage and accurate expected results.
• Confirm README examples match implementation behavior.

Possibly related PRs

• feat(arrays, puzzles, matrix): lucky number in a matrix #115 — Adds a lucky_numbers implementation for the same puzzle (related implementation overlap; compare behaviors and tests).

Poem

🐇 I hopped through rows and columns with delight,
Seeking minima that spark a max's light,
A greedy nibble, a careful little plot,
I found the lucky numbers—tucked in a spot! ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a lucky number algorithm for matrices, which aligns with the changeset.
Description check	✅ Passed	The PR description follows the template structure with a clear problem description and all checklist items addressed, indicating comprehensive compliance with contribution guidelines.

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📜 Recent review details

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Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1e71628 and 03e8a32.

⛔ Files ignored due to path filters (1)

• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_proof_of_contradiction.png is excluded by !**/*.png

📒 Files selected for processing (3)

• puzzles/arrays/lucky_numbers_in_a_matrix/README.md (1 hunks)
• puzzles/arrays/lucky_numbers_in_a_matrix/__init__.py (1 hunks)
• puzzles/arrays/lucky_numbers_in_a_matrix/test_lucky_numbers_in_a_matrix.py (1 hunks)

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (2)

DIRECTORY.md (1)

487-488: Lucky Numbers entry looks correct; markdownlint indent warning is likely stylistic

The new directory entries and test link follow the existing patterns for puzzles/arrays and point to the expected path. The markdownlint MD007 warning about indentation (2 vs 4 spaces) conflicts with the indentation already used by neighboring items in this section, so it’s more of a style/configuration concern than a content issue. If your pipeline enforces MD007 strictly, you may want to either tweak this list’s indentation globally or relax that rule for this file, rather than changing just these two lines.

puzzles/arrays/lucky_numbers_in_a_matrix/test_lucky_numbers_in_a_matrix.py (1)

1-40: Solid parameterized coverage of the lucky_numbers behavior

The tests exercise the core cases well: multiple 3×3 and 4×4 matrices with and without lucky numbers, plus the 1×1 edge case, all matching the definition used in the implementation. Using parameterized.expand keeps the suite compact and readable. If you want to push coverage slightly further, you could add an explicitly non-square rectangular case (e.g., 2×3) to demonstrate that the logic doesn’t rely on squareness, but that’s optional given the current constraints.

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 6da8745 and 1e71628.

⛔ Files ignored due to path filters (19)

• puzzles/arrays/lucky_numbers_in_a_matrix/images/examples/lucky_numbers_in_a_matrix_example_1.png is excluded by !**/*.png
• puzzles/arrays/lucky_numbers_in_a_matrix/images/examples/lucky_numbers_in_a_matrix_example_2.png is excluded by !**/*.png
• puzzles/arrays/lucky_numbers_in_a_matrix/images/examples/lucky_numbers_in_a_matrix_example_3.png is excluded by !**/*.png
• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_in_a_matrix_solution_1.png is excluded by !**/*.png
• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_in_a_matrix_solution_10.png is excluded by !**/*.png
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• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_in_a_matrix_solution_12.png is excluded by !**/*.png
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• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_in_a_matrix_solution_15.png is excluded by !**/*.png
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• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_in_a_matrix_solution_8.png is excluded by !**/*.png
• puzzles/arrays/lucky_numbers_in_a_matrix/images/solutions/lucky_numbers_in_a_matrix_solution_9.png is excluded by !**/*.png

📒 Files selected for processing (4)

• DIRECTORY.md (1 hunks)
• puzzles/arrays/lucky_numbers_in_a_matrix/README.md (1 hunks)
• puzzles/arrays/lucky_numbers_in_a_matrix/__init__.py (1 hunks)
• puzzles/arrays/lucky_numbers_in_a_matrix/test_lucky_numbers_in_a_matrix.py (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

puzzles/arrays/lucky_numbers_in_a_matrix/test_lucky_numbers_in_a_matrix.py (1)

puzzles/arrays/lucky_numbers_in_a_matrix/__init__.py (1)

• lucky_numbers (4-54)

🪛 LanguageTool

puzzles/arrays/lucky_numbers_in_a_matrix/README.md

[grammar] ~56-~56: Ensure spelling is correct
Context: ...est_min or c_smallest_max. Otherwise if now matching value is found, we return an e...

(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)

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[style] ~81-~81: Using many exclamation marks might seem excessive (in this case: 15 exclamation marks for a text that’s 5161 characters long)
Context: ...cky_numbers_in_a_matrix_solution_1.png) ![Solution 15](./images/solutions/lucky_n...

(EN_EXCESSIVE_EXCLAMATION)

🪛 markdownlint-cli2 (0.18.1)

DIRECTORY.md

487-487: Unordered list indentation
Expected: 2; Actual: 4

(MD007, ul-indent)

---

488-488: Unordered list indentation
Expected: 4; Actual: 6

(MD007, ul-indent)

puzzles/arrays/lucky_numbers_in_a_matrix/README.md

39-39: Multiple spaces after blockquote symbol

(MD027, no-multiple-space-blockquote)

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45-45: Multiple spaces after blockquote symbol

(MD027, no-multiple-space-blockquote)