Sudoku: Difference between revisions

=={{header|Nim}}==

{{trans|Kotlin}}

<lang nim>{.this: self.}

type

Sudoku = ref object

grid : array[81, int]

solved : bool

proc `$`(self: Sudoku): string =

var sb: string = ""

for i in 0..8:

for j in 0..8:

sb &= $grid[i * 9 + j]

sb &= " "

if j == 2 or j == 5: sb &= "| "

sb &= "\n"

if i == 2 or i == 5: sb &= "------+------+------\n"

sb

proc init(self: Sudoku, rows: array[9, string]) =

for i in 0..8:

for j in 0..8:

grid[9 * i + j] = rows[i][j].int - '0'.int

proc checkValidity(self: Sudoku, v, x, y: int): bool =

for i in 0..8:

if grid[y * 9 + i] == v or grid[i * 9 + x] == v: return false

var startX = (x div 3) * 3

var startY = (y div 3) * 3

for i in startY..startY + 2:

for j in startX..startX + 2:

if grid[i * 9 + j] == v: return false

result = true

proc placeNumber(self: Sudoku, pos: int) =

if solved: return

if pos == 81:

solved = true

return

if grid[pos] > 0:

placeNumber(pos + 1)

return

for n in 1..9:

if checkValidity(n, pos mod 9, pos div 9):

grid[pos] = n

placeNumber(pos + 1)

if solved: return

grid[pos] = 0

proc solve(self: Sudoku) =

echo "Starting grid:\n\n", $self

placeNumber(0)

if solved:

echo "Solution:\n\n", $self

else:

echo "Unsolvable!"

var rows = ["850002400",

"720000009",

"004000000",

"000107002",

"305000900",

"040000000",

"000080070",

"017000000",

"000036040"]

var puzzle = Sudoku()

puzzle.init(rows)

puzzle.solve()</lang>

{{out}}

<pre>Starting grid:

8 5 0 | 0 0 2 | 4 0 0

7 2 0 | 0 0 0 | 0 0 9

0 0 4 | 0 0 0 | 0 0 0

------+-------+------

0 0 0 | 1 0 7 | 0 0 2

3 0 5 | 0 0 0 | 9 0 0

0 4 0 | 0 0 0 | 0 0 0

------+-------+------

0 0 0 | 0 8 0 | 0 7 0

0 1 7 | 0 0 0 | 0 0 0

0 0 0 | 0 3 6 | 0 4 0

Solution:

8 5 9 | 6 1 2 | 4 3 7

7 2 3 | 8 5 4 | 1 6 9

1 6 4 | 3 7 9 | 5 2 8

------+-------+------

9 8 6 | 1 4 7 | 3 5 2

3 7 5 | 2 6 8 | 9 1 4

2 4 1 | 5 9 3 | 7 8 6

------+-------+------

4 3 2 | 9 8 1 | 6 7 5

6 1 7 | 4 2 5 | 8 9 3

5 9 8 | 7 3 6 | 2 4 1</pre>