def solveSudoku(puzzle):"""Solves a Sudoku puzzle.
Args:puzzle (list): A list of strings representing the Sudoku puzzle.
Returns:list: A list of strings representing the solved Sudoku puzzle."""
# Iterate over the rows, columns, and subgrids.for row in range(9):for col in range(9):if puzzle[row][col] == '.':# Check if the number is already in the row, column, or subgrid.for i in range(9):if puzzle[row][i] != '.' and puzzle[i][col] != '.' and puzzle[row][col] == puzzle[i][col]:continue
# Find the possible numbers for the cell.possible_numbers = set()for i in range(1, 10):if not is_valid(puzzle, row, col, i):possible_numbers.add(i)
# Try each possible number.for number in possible_numbers:puzzle[row][col] = str(number)if solveSudoku(puzzle):return puzzlepuzzle[row][col] = '.'
# If no solution is found, return the original puzzle.return puzzle

# Helper function to check if a number is valid for a cell.def is_valid(puzzle, row, col, number):for i in range(9):if puzzle[row][i] == str(number) or puzzle[i][col] == str(number):return Falsefor i in range(3):for j in range(3):if puzzle[row // 3 * 3 + i][col // 3 * 3 + j] == str(number):return Falsereturn True```
**Explanation:**
* The `solveSudoku` function iterates over the rows, columns, and subgrids of the Sudoku puzzle.* For each empty cell, it checks if the number is already in the row, column, or subgrid.* It then finds the possible numbers for the cell and tries each one.* If a solution is found, it returns the solved puzzle. Otherwise, it returns the original puzzle.* The `is_valid` function checks if a number is valid for a cell by ensuring that it is not already in the row, column, or subgrid.
**Example Usage:**
```python# Example Sudoku puzzle.puzzle = [['5', '3', '.', '.', '7', '8', '.', '.', '.'],['.', '7', '4', '6', '.', '5', '8', '9', '.'],['.', '.', '8', '.', '9', '1', '.', '6', '.'],// ... Rest of the puzzle.]
# Solve the Sudoku puzzle.solution = solveSudoku(puzzle)
# Print the solved puzzle.print(solution)```