A Sudoku solver implemented in Rust displays a completed 9x9 puzzle grid as a console output, replacing empty cells with solved digits. The code models the board as a 2D array of characters and converts it to integers, then uses a backtracking algorithm with constraint propagation to find the solution. The `solve_step` function recursively tries candidate numbers, while `get_possible_numbers` checks row, column, and 3x3 subgrid constraints to filter valid options. The final result prints the solved board row by row using standard Rust formatting and I/O operations.