Sudoku Solver Program in Python

     Sudoku is a number puzzle which makes the arrangement in particular order in a square.

Logic:

• Let us consider 1 to 9 number.
• Plan a table for 9 rows and 9 columns.
• Each 3x3 row and column’s consider a part. So there are 9 parts.
• There are two things to be considered.
• First, each row and each column should have the number 1 to 9 at least once. But same number should not be repeated.
• Next, each part should have the number 1 to 9.

Python implementation:

def ch_valid(board1, s_row, s_col, n):

    for i in range(9):

        if board1[s_row][i] == n or board1[i][s_col] == n:

            return False

    start_row, start_col = 3 * (s_row // 3), 3 * (s_col // 3)

    for i in range(3):

        for j in range(3):

            if board1[start_row + i][start_col + j] == n:

                return False

    return True

def solveit_sudoku(board1):

    for s_row in range(9):

        for s_col in range(9):

            if board1[s_row][s_col] == 0:

                for n in range(1, 10):

                    if ch_valid(board1, s_row, s_col, n):

                        board1[s_row][s_col] = n

                        if solveit_sudoku(board1):

                            return True

                        board1[s_row][s_col] = 0

                return False

    return True

def display_board(board1):

    for s_row in board1:

        print(" ".join(str(n) for n in s_row))

def main():

    board1 = [

        [0, 3, 4, 0, 0, 8, 0, 1, 0],

        [6, 0, 2, 1, 0, 5, 0, 4, 0],

        [0, 9, 0, 3, 0, 2, 0, 6, 0],

        [0, 5, 0, 7, 6, 0, 0, 0, 3],

        [4, 0, 6, 8, 0, 0, 7, 0, 1],

        [7, 0, 3, 0, 0, 4, 8, 0, 6],

        [0, 6, 0, 5, 0, 7, 0, 8, 0],

        [0, 8, 0, 4, 0, 9, 6, 0, 5],

        [0, 0, 5, 2, 0, 0, 1, 7, 0]

    ]

    print("The Original Sudoku is shown in output:")

    display_board(board1)

    print("\nSolved Sudoku is given below:")

    if solveit_sudoku(board1):

        display_board(board1)

    else:

        print("No solution exists")

if __name__ == "__main__":

    main()

Output:

C:\raji>py sudoku.py

The Original Sudoku is shown in output:

0 3 4 0 0 8 0 1 0

6 0 2 1 0 5 0 4 0

0 9 0 3 0 2 0 6 0

0 5 0 7 6 0 0 0 3

4 0 6 8 0 0 7 0 1

7 0 3 0 0 4 8 0 6

0 6 0 5 0 7 0 8 0

0 8 0 4 0 9 6 0 5

0 0 5 2 0 0 1 7 0

Solved Sudoku is given below:

5 3 4 6 7 8 9 1 2

6 7 2 1 9 5 3 4 8

1 9 8 3 4 2 5 6 7

8 5 9 7 6 1 4 2 3

4 2 6 8 5 3 7 9 1

7 1 3 9 2 4 8 5 6

9 6 1 5 3 7 2 8 4

2 8 7 4 1 9 6 3 5

3 4 5 2 8 6 1 7 9

That’s all. The implementation of sudoku in python was written successfully. Keep coding!!!