## Click to expand!

```
function row(board,n)
#returns values in row n of board
return @view board[6*n-5:6*n]
end
function col(board,n)
#returns values in col n of board
ct = n:6:36
ntuple(i->board[ct[i]], 6)
end
const q = ((1,2,3,7,8,9,13,14,15),(4,5,6,10,11,12,16,17,18),(19,20,21,25,26,27,31,32,33),(22,23,24,28,29,30,34,35,36))
function quadrant(board,n)
qn = q[n]
return ntuple(i->board[qn[i]], 9)
end
# function row(board,n)
# #returns values in row n of board
# return board[6*n-5:6*n]
# end
#
# function col(board,n)
# #returns values in col n of board
# if n == 6
# return [board[i] for i in [6,12,18,24,30,36]]
# else
# return [board[i] for i in 1:36 if i%6 == n]
# end
# end
#
# function quadrant(board,n)
# q = [[1,2,3,7,8,9,13,14,15],[4,5,6,10,11,12,16,17,18],[19,20,21,25,26,27,31,32,33],[22,23,24,28,29,30,34,35,36]]
# return [board[i] for i in q[n]]
# end
#Solving Numoku Puzzle 20002
#https://twitter.com/1to9puzzle/status/1212782433612861441
const BOARD = [4,2,8,0,0,0,0,0,0,9,0,0,0,0,7,0,0,0,0,0,0,4,0,0,0,0,5,0,0,0,0,0,0,5,6,2]
function count(mylist,thing)
output = 0
for i in mylist
if i == thing
output += 1
end
end
output
end
const NUMS = 1:9
const NUMBLANKS = count(BOARD,0)
#print(NUMBLANKS)
const output = copy(BOARD)
function populate_board(solution_board)
copyto!(output, BOARD)
ind = 1
for i in 1:36
if output[i] == 0
output[i] = solution_board[ind]
ind +=1
end
end
output
end
function repeat(mylist)
for n in mylist
if n != 0 && count(mylist,n)>1
return true
end
end
return false
end
function print_board(solution_board)
#board = populate_board(solution_board)
print()
for i in 1:36
if i % 6 == 0
println(solution_board[i])
else
print(solution_board[i])
print(' ')
end
end
println() #blank line
end
# rboard = rand(1:9,1,36)
# print_board(rboard)
# println(row(rboard,2))
#println(col(rboard,6))
# println(sum(quadrant(rboard,2)))
function check_no_conflicts(solution_board)
#Returns False if there ARE conflicts
for j in 1:6
this_row = row(solution_board,j)
if repeat(this_row)
#println("repeat row",j)
return false
end
if count(this_row,0) == 0 && sum(this_row) != 30
return false
end
this_col = col(solution_board,j)
#println("col count 0's ",count(this_col,0))
if repeat(this_col)
#println("repeat col",j)
return false
end
if (count(this_col,0) == 0) && (sum(this_col) != 30)
#println("col sum",j)
return false
end
end
for i in 1:4
this_quad = quadrant(solution_board,i)
if repeat(this_quad)
return false
end
for j in 1:9
if count(this_quad,0) == 0 && count(this_quad,j) != 1
#println("quad",n)
return false
end
end
end
return true
end
# rboard = rand(1:9,1,36)
# print_board(rboard)
# println(check_no_conflicts(rboard))
const board = [4, 2, 8, 7, 3, 6, 1, 5, 3, 9, 8, 4, 6, 9, 7, 2, 5, 1, 2, 3, 6, 4, 7, 8, 8, 4, 5, 3, 1, 9, 9, 7, 1, 5, 6, 2]
println(check_no_conflicts(board))
function solve(values, size)
solution_list = zeros(size)
function extend_solution(position)
for value in values
solution_list[position] = value
solution = populate_board(solution_list)
#print_board(solution)
if check_no_conflicts(solution)
#This change was the key. It wasn't returning the
#solution up to the end.
if position >= size
return solution
end
new_solution = extend_solution(position+1)
if new_solution != nothing
return new_solution
end
else
solution_list[position] = 0
if position < size
solution_list[position+1] = 0
end
if value == values[length(values)]
#println("end of values")
if position > 1
solution_list[position-1] = 0
end
end
end
end
nothing
end
extend_solution(1)
end
#board1 = create_board(BOARD)
#print_board(board1)
function main()
soln = solve(NUMS,NUMBLANKS)
# print_board(soln)
end
main()
using BenchmarkTools
@btime main()
```