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| def solve_sudoku(grid):
# Find an empty cell (with value 0)
for i in range(9):
for j in range(9):
if grid[i][j] == 0:
# Try all possible numbers
for num in range(1, 10):
if is_valid(grid, i, j, num):
# Try this number
grid[i][j] = num
# Recursively solve the rest
if solve_sudoku(grid):
return True
# Backtrack if solution not found
grid[i][j] = 0
# No valid number found
return False
# All cells filled
return True
def is_valid(grid, row, col, num):
# Check row
if num in grid[row]:
return False
# Check column
for i in range(9):
if grid[i][col] == num:
return False
# Check 3x3 subgrid
start_row, start_col = 3 * (row // 3), 3 * (col // 3)
for i in range(3):
for j in range(3):
if grid[start_row + i][start_col + j] == num:
return False
return True
def print_grid(grid):
for i in range(9):
if i % 3 == 0 and i != 0:
print("- - - - - - - - - - -")
for j in range(9):
if j % 3 == 0 and j != 0:
print("|", end=" ")
print(grid[i][j] if grid[i][j] != 0 else ".", end=" ")
print()
def grid_to_string(grid):
return ''.join(''.join(str(num) for num in row) for row in grid)
# Sudoku grid
sudoku = [
[0,8,0,0,0,0,0,7,0],
[7,0,2,0,0,0,0,5,1],
[0,6,0,0,0,7,9,0,8],
[0,5,0,0,0,2,0,0,4],
[1,0,0,0,0,0,2,3,0],
[2,0,4,0,1,3,0,8,0],
[0,0,5,0,8,9,1,0,0],
[9,0,0,0,0,0,8,0,0],
[0,1,7,2,5,6,4,0,3]
]
print("Original Sudoku:")
print_grid(sudoku)
original_str = grid_to_string(sudoku)
print("\nOriginal as string:", original_str)
print("\nSolving...\n")
if solve_sudoku(sudoku):
print("Solved Sudoku:")
print_grid(sudoku)
solved_str = grid_to_string(sudoku)
print("\nSolved as string:", solved_str)
else:
print("No solution exists for this Sudoku puzzle.")
|
