ssolver.py

# Suduko Solver
# recursive solution by Prof Thorsten Altenkirch
# https://www.youtube.com/watch?v=G_UYXzGuqvM&t=3s
#
# Roger Banks
# 18 Feb 2020

import numpy as np

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

def possible(y,x,n) :
	global grid
	for i in range(0,9) :
		if grid[y][i] == n :
			return False
	for i in range(0,9) :
		if grid[i][x] == n :
			return False
	x0 = (x // 3) * 3
	y0 = (y // 3) * 3
	for i in range(0,3) :
		for j in range(0,3) :
			if grid[y0+i][x0+j] == n :
				return False
	return True

def solve() :
	global grid
	for y in range(9) :
		for x in range(9) :
			if grid[y][x] == 0 :
				for n in range(1,10) :
					if possible(y,x,n) :
						grid[y][x] = n
						solve()
						grid[y][x] = 0
				return

	print(np.matrix(grid))
	input("More?")

solve()