feat(arrays): set matrix zeroes

[BrianLusina]

Describe your change:

Adds an algorithm to sets all the values of an n*m matrix to zero if any value in a row or column is zero.

• 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.

Summary by CodeRabbit

• New Features

  • Added a matrix utility that zeroes entire rows and columns when any element is zero (in-place behavior preserved).

• Documentation

  • Added README describing the problem, constraints and illustrative examples.

• Tests

  • Added a test suite with five cases covering single zeros, multiple zeros, no-op and mixed scenarios.

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Adds a new "Set Matrix Zero" feature: a public function that zeros matrix rows and columns in-place using first row/column markers, plus documentation and unit tests. No other codepaths were modified.

Changes

Cohort / File(s)	Summary
Documentation DIRECTORY.md, datastructures/arrays/matrix/settozero/README.md	Added directory entry and README describing the Set Matrix Zero problem, constraints, examples, and algorithm overview.
Implementation datastructures/arrays/matrix/settozero/__init__.py	New public function set_matrix_zeros(mat: List[List[int]]) -> List[List[int]] that marks and zeros rows/columns in-place using the first row/column as markers; handles empty matrices and first-row/column edge cases; O(rows×cols) time, O(1) extra space.
Tests datastructures/arrays/matrix/settozero/test_set_matrix_zero.py	New unittest module with five cases exercising single-zero propagation, no-op, multiple zeros, and mixed scenarios; includes test runner entry point.

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant set_matrix_zeros
    participant Matrix

    Caller->>set_matrix_zeros: call(mat)
    set_matrix_zeros->>set_matrix_zeros: validate input (empty?)
    set_matrix_zeros->>Matrix: scan first row & first column for zeros
    note right of set_matrix_zeros: record flags for first row/col
    set_matrix_zeros->>Matrix: mark rows/cols by writing to first row/col
    set_matrix_zeros->>Matrix: zero interior cells based on markers
    set_matrix_zeros->>Matrix: zero first row if flagged
    set_matrix_zeros->>Matrix: zero first column if flagged
    set_matrix_zeros->>Caller: return modified matrix

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

• Review marker logic and order of operations in __init__.py (ensuring original first row/column flags are preserved before marking).
• Validate edge-case handling for empty matrices and single-row/column matrices.
• Verify test coverage in test_set_matrix_zero.py matches described scenarios.

Poem

🐰 I hopped through rows and columns wide,
Marked the places where zeros hide,
A gentle nudge—no extra space,
Rows and columns cleared with grace,
Hooray, the matrix sleeps—zeros inside.

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 16.67% 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 'feat(arrays): set matrix zeroes' clearly and concisely describes the main change: adding a set matrix zeroes algorithm to the arrays module.
Description check	✅ Passed	The PR description includes the required template sections, covers the main change, and confirms completion of all checklist items as per repository 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 04d315f and 0b63041.

📒 Files selected for processing (2)

• datastructures/arrays/matrix/settozero/README.md (1 hunks)
• datastructures/arrays/matrix/settozero/__init__.py (1 hunks)

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (1)

DIRECTORY.md (1)

190-192: Consider adjusting markdown indentation for consistency.

The markdown linter flags the indentation here as non-standard (using 4/6/8 spaces instead of the expected 2/4/6). While this doesn't affect functionality, aligning with standard markdown conventions improves consistency.

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 9f5abb3 and 04d315f.

⛔ Files ignored due to path filters (3)

• datastructures/arrays/matrix/settozero/images/set_matrix_zero_example_one.png is excluded by !**/*.png
• datastructures/arrays/matrix/settozero/images/set_matrix_zero_example_three.png is excluded by !**/*.png
• datastructures/arrays/matrix/settozero/images/set_matrix_zero_example_two.png is excluded by !**/*.png

📒 Files selected for processing (4)

• DIRECTORY.md (1 hunks)
• datastructures/arrays/matrix/settozero/README.md (1 hunks)
• datastructures/arrays/matrix/settozero/__init__.py (1 hunks)
• datastructures/arrays/matrix/settozero/test_set_matrix_zero.py (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

datastructures/arrays/matrix/settozero/test_set_matrix_zero.py (1)

datastructures/arrays/matrix/settozero/__init__.py (1)

• set_matrix_zeros (4-55)

🪛 markdownlint-cli2 (0.18.1)

DIRECTORY.md

190-190: Unordered list indentation
Expected: 2; Actual: 4

(MD007, ul-indent)

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191-191: Unordered list indentation
Expected: 4; Actual: 6

(MD007, ul-indent)

---

192-192: Unordered list indentation
Expected: 6; Actual: 8

(MD007, ul-indent)

🔇 Additional comments (3)

datastructures/arrays/matrix/settozero/__init__.py (2)

19-27: LGTM! Efficient edge case and marker detection.

The empty matrix check prevents issues with edge cases, and using any() with generator expressions for detecting zeros in the first row/column is memory-efficient.

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29-53: Excellent O(1) space implementation!

The algorithm correctly implements the standard in-place solution by using the first row and column as markers. The three-phase approach (mark interior → apply to interior → handle boundaries) is the right way to avoid corrupting markers prematurely.

datastructures/arrays/matrix/settozero/test_set_matrix_zero.py (1)

5-34: Comprehensive test coverage!

The five test cases provide excellent coverage:

• Single zero propagation (test_1, test_4)
• No-op scenario with no zeros (test_2)
• Multiple zeros with complex patterns (test_3, test_5)
• Various matrix dimensions (3x3, 3x4, 5x5)

All expected outputs are correct.