🧩 Backtracking Sudoku Solver

A simple yet powerful Sudoku solver built in Python using the backtracking algorithm.
It checks all possible numbers for each empty cell and backtracks when a number leads to a dead end — continuing recursively until the puzzle is solved.

🚀 How It Works

1. Row & Column Validation:
   Checks if the chosen number already exists in the same row or column.

2. 3x3 Subgrid Validation:
   Calculates the top-left corner of each 3x3 box and ensures no duplicates exist.

3. Backtracking Algorithm:

   • Tries placing numbers 1–9 in each empty cell.
   • If a valid placement leads to a full solution, it returns True.
   • Otherwise, it resets the cell to 0 and tries the next number.