[FEATURE REQUEST] Add Sudoku Solver using Backtracking

[Shewale41]

What would you like to Propose?

Title: Add Sudoku Solver using Backtracking

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🧠 Overview

I’d like to contribute a Sudoku Solver algorithm using the Backtracking technique. This algorithm systematically explores all valid placements of digits in a 9×9 Sudoku grid until it finds a valid solution that satisfies all Sudoku constraints.

🧩 Problem Description

Given a partially filled 9×9 Sudoku board, fill all empty cells (represented by 0) such that every row, column, and 3×3 subgrid contains the digits 1 through 9 exactly once.

📂 Implementation Details

• Folder: src/main/java/com/thealgorithms/backtracking/
• Filename: SudokuSolver.java
• Approach: Depth-first backtracking algorithm that tries valid numbers recursively and backtracks on invalid placements.

✅ Expected Deliverables

• Clean, modular implementation (e.g., isValid(), solveSudoku() methods).
• Example main() method demonstrating functionality.
• Unit tests validating correctness on solvable and unsolvable grids.
• Clear in-code documentation and time complexity notes.

🧑‍💻 Additional Notes

Backtracking is one of the most intuitive ways to solve Sudoku and a great educational addition to the repository. I have a working version ready and would like to open a PR once this issue is approved.

Issue details

🧩 Problem Description

Given a partially filled 9×9 Sudoku board, fill all empty cells (represented by 0) such that every row, column, and 3×3 subgrid contains the digits 1 through 9 exactly once.

Additional Information

No response

[Akhilesh-0529]

I would like to be assigned this issue!

[Suhas-30]

I would like to work on this issue. Could you please clarify whether the given partially filled board is always valid, or if it may contain invalid Sudoku boards as well?