https://github.com/vish501/sudoku-solver

Sudoku Solver using Backtracking and Recursion
https://github.com/vish501/sudoku-solver

backtracking recursion sudoku sudoku-solver

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Sudoku Solver using Backtracking and Recursion

• Host: GitHub
• URL: https://github.com/vish501/sudoku-solver
• Owner: Vish501
• Created: 2023-12-28T11:56:03.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2024-12-05T09:16:16.000Z (5 months ago)
• Last Synced: 2025-03-19T05:44:19.722Z (about 2 months ago)
• Topics: backtracking, recursion, sudoku, sudoku-solver
• Language: Python
• Homepage:
• Size: 7.81 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Sudoku Solver (Backtracking and Recursion)

This Python program utilizes backtracking and recursion to solve Sudoku puzzles.

**How it Works:**

1. **Initialization:**

   - Takes a 9x9 Sudoku grid as input (represented as a list of lists).

   - Empty cells are represented by -1.

2. **Find Empty Cell:**

   - A helper function efficiently locates the next empty cell in the grid.

3. **Backtracking Algorithm:**

   - If no empty cells are found, the current grid is a valid solution, and the program returns True.

   - For each possible number (1-9):

      - Place the number in the empty cell.

      - Recursively call the solver to check if the updated grid is valid.

      - If the recursive call returns True, the current grid is solved, and the program returns True.

      - If the recursive call returns False, remove the number from the cell and try another number.

   - If no number leads to a valid solution, backtrack and try different numbers in previous empty cells.

4. **Validation:**

   - Checks if a number is valid in a specific cell by ensuring it doesn't violate Sudoku rules:

      - No duplicates in the same row.

      - No duplicates in the same column.

      - No duplicates in the same 3x3 subgrid.

**Usage:**

1. **Prepare Input:**

   - Create a 9x9 list of lists representing the Sudoku grid.

   - Use -1 to represent empty cells.

2. **Run the Program:**

   - Call the `solve_sudoku()` function with the input grid.

3. **Output:**

   - Sudoku grid solved, in place.

**Example:**

```python

grid = [

        [3, 9, -1,   -1, 5, -1,   -1, -1, -1],

        [-1, -1, -1,   2, -1, -1,   -1, -1, 5],

        [-1, -1, -1,   7, 1, 9,   -1, 8, -1],

        [-1, 5, -1,   -1, 6, 8,   -1, -1, -1],

        [2, -1, 6,   -1, -1, 3,   -1, -1, -1],

        [-1, -1, -1,   -1, -1, -1,   -1, -1, 4],

        [5, -1, -1,   -1, -1, -1,   -1, -1, -1],

        [6, 7, -1,   1, -1, 5,   -1, 4, -1],

        [1, -1, 9,   -1, -1, -1,   2, -1, -1]

    ]

    

solve_sudoku(puzzle)

print(puzzle)