sudoku-solver.py

import time 

board = [
    [7,8,0,4,0,0,1,2,0],
    [6,0,0,0,7,5,0,0,9],
    [0,0,0,6,0,1,0,7,8],
    [0,0,7,0,4,0,2,6,0],
    [0,0,1,0,5,0,9,3,0],
    [9,0,4,0,6,0,0,0,5],
    [0,7,0,3,0,0,0,1,2],
    [1,2,0,0,0,7,4,0,0],
    [0,4,9,2,0,6,0,0,7]
]

def print_board(bo):
	for i in range(len(bo)):
		if i % 3 == 0 and i != 0:
			print('_ _ _ _ _ _ _ _ _ _ ')
		
		for j in range(len(bo[0])):
			if j % 3 == 0 and j != 0:
				print('|' , end='')
				
			if j == 8:
				print(bo[i][j])
			else:
				print(str(bo[i][j]) + ' ' , end='')
			

def find_empty(bo):
	for i in range(len(bo)):
		for j in range(len(bo[0])):
			if bo[i][j] == 0:
				return (i , j)
	return None
	
				
def valid(bo , num , pos):
	for i in range(len(bo[0])):
		if bo[pos[0]][i] == num and pos[1] != i:
			return False
			
	for i in range(len(bo)):
		if bo[i][pos[1]] == num and pos[0] != i:
			return False
			
	board_x = pos[1] //3
	board_y = pos[0] // 3
	for i in range(board_y * 3 , board_y * 3 + 3):
		for j in range(board_x*3 , board_x*3+3):
			if bo[i][j] == num and (i , j) != pos:
				return False
	return True
		
		
		
		
def solve(bo):
		print_board(bo)
		print('\n\n')
		find = find_empty(bo)
		
		if not find:
			return True
		else:
			row,col = find
			
		for i in range(1 , 10):
			if valid(bo , i , (row , col)):
				bo[row][col] = i
			
				if solve(bo):
					return True
					
				bo[row][col] = 0
			
		return False
			
		
		
		
		
print_board(board)

print('\n SOLVING ....................')
now = time.time()
print('\n\n\n-----------------------------------\n\n\n')
solve(board)
print('\\n\n-----------------------------------\n\n\n Board Solved \n \n')
end  = time.time()
print_board(board)
print(f'\nTook {end - now} seconds to complete')