Peaceful chess queen armies: Difference between revisions

=={{header|Nim}}==

{{trans|Kotlin}}

Almost a direct translation except for "printBoard" where we have chosen to use a sequence of sequences to simplify the code.

<lang Nim>import sequtils, strformat

type

Piece {.pure.} = enum Empty, Black, White

Position = tuple[x, y: int]

func isAttacking(queen, pos: Position): bool =

queen.x == pos.x or queen.y == pos.y or abs(queen.x - pos.x) == abs(queen.y - pos.y)

func place(m, n: int; blackQueens, whiteQueens: var seq[Position]): bool =

if m == 0: return true

var placingBlack = true

for i in 0..<n:

for j in 0..<n:

block inner:

let pos: Position = (i, j)

for queen in blackQueens:

if queen == pos or not placingBlack and queen.isAttacking(pos):

break inner

for queen in whiteQueens:

if queen == pos or placingBlack and queen.isAttacking(pos):

break inner

if placingBlack:

blackQueens.add pos

else:

whiteQueens.add pos

if place(m - 1, n, blackQueens, whiteQueens): return true

discard blackQueens.pop()

discard whiteQueens.pop()

placingBlack = not placingBlack

if not placingBlack:

discard blackQueens.pop()

proc printBoard(n: int; blackQueens, whiteQueens: seq[Position]) =

var board = newSeqWith(n, newSeq[Piece](n)) # Initialized to Empty.

for queen in blackQueens:

board[queen.x][queen.y] = Black

for queen in whiteQueens:

board[queen.x][queen.y] = White

for i in 0..<n:

for j in 0..<n:

stdout.write case board[i][j]

of Black: "B "

of White: "W "

of Empty: (if (i and 1) == (j and 1): "• " else: "◦ ")

stdout.write '\n'

echo ""

const Nms = [(2, 1), (3, 1), (3, 2), (4, 1), (4, 2), (4, 3),

(5, 1), (5, 2), (5, 3), (5, 4), (5, 5),

(6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6),

(7, 1), (7, 2), (7, 3), (7, 4), (7, 5), (7, 6), (7, 7)]

for (n, m) in Nms:

echo &"{m} black and {m} white queens on a {n} x {n} board:"

var blackQueens, whiteQueens: seq[Position]

if place(m, n, blackQueens, whiteQueens):

printBoard(n, blackQueens, whiteQueens)

else:

echo "No solution exists.\n"</lang>

{{out}}

<pre>1 black and 1 white queens on a 2 x 2 board:

No solution exists.

1 black and 1 white queens on a 3 x 3 board:

B ◦ •

◦ • W

• ◦ •

2 black and 2 white queens on a 3 x 3 board:

No solution exists.

1 black and 1 white queens on a 4 x 4 board:

B ◦ • ◦

◦ • W •

• ◦ • ◦

◦ • ◦ •

2 black and 2 white queens on a 4 x 4 board:

B ◦ • ◦

◦ • W •

B ◦ • ◦

◦ • W •

3 black and 3 white queens on a 4 x 4 board:

No solution exists.

1 black and 1 white queens on a 5 x 5 board:

B ◦ • ◦ •

◦ • W • ◦

• ◦ • ◦ •

◦ • ◦ • ◦

• ◦ • ◦ •

2 black and 2 white queens on a 5 x 5 board:

B ◦ • ◦ B

◦ • W • ◦

• W • ◦ •

◦ • ◦ • ◦

• ◦ • ◦ •

3 black and 3 white queens on a 5 x 5 board:

B ◦ • ◦ B

◦ • W • ◦

• W • ◦ •

◦ • ◦ B ◦

• W • ◦ •

4 black and 4 white queens on a 5 x 5 board:

• B • B •

◦ • ◦ • B

W ◦ W ◦ •

◦ • ◦ • B

W ◦ W ◦ •

5 black and 5 white queens on a 5 x 5 board:

No solution exists.

1 black and 1 white queens on a 6 x 6 board:

B ◦ • ◦ • ◦

◦ • W • ◦ •

• ◦ • ◦ • ◦

◦ • ◦ • ◦ •

• ◦ • ◦ • ◦

◦ • ◦ • ◦ •

2 black and 2 white queens on a 6 x 6 board:

B ◦ • ◦ B ◦

◦ • W • ◦ •

• W • ◦ • ◦

◦ • ◦ • ◦ •

• ◦ • ◦ • ◦

◦ • ◦ • ◦ •

3 black and 3 white queens on a 6 x 6 board:

B ◦ • ◦ B B

◦ • W • ◦ •

• W • ◦ • ◦

◦ • ◦ • ◦ •

• ◦ W ◦ • ◦

◦ • ◦ • ◦ •

4 black and 4 white queens on a 6 x 6 board:

B ◦ • ◦ B B

◦ • W • ◦ •

• W • ◦ • ◦

◦ • ◦ • ◦ B

• ◦ W W • ◦

◦ • ◦ • ◦ •

5 black and 5 white queens on a 6 x 6 board:

• B • ◦ B ◦

◦ • ◦ B ◦ B

W ◦ • ◦ • ◦

W • W • ◦ •

• ◦ • ◦ • B

W • W • ◦ •

6 black and 6 white queens on a 6 x 6 board:

No solution exists.

1 black and 1 white queens on a 7 x 7 board:

B ◦ • ◦ • ◦ •

◦ • W • ◦ • ◦

• ◦ • ◦ • ◦ •

◦ • ◦ • ◦ • ◦

• ◦ • ◦ • ◦ •

◦ • ◦ • ◦ • ◦

• ◦ • ◦ • ◦ •

2 black and 2 white queens on a 7 x 7 board:

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

• ◦ • ◦ • ◦ •

◦ • ◦ • ◦ • ◦

• ◦ • ◦ • ◦ •

◦ • ◦ • ◦ • ◦

• ◦ • ◦ • ◦ •

3 black and 3 white queens on a 7 x 7 board:

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

B ◦ • ◦ • ◦ •

◦ • W • ◦ • ◦

• ◦ • ◦ • ◦ •

◦ • ◦ • ◦ • ◦

• ◦ • ◦ • ◦ •

4 black and 4 white queens on a 7 x 7 board:

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

• ◦ • ◦ • ◦ •

◦ • ◦ • ◦ • ◦

• ◦ • ◦ • ◦ •

5 black and 5 white queens on a 7 x 7 board:

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

B ◦ • ◦ • ◦ •

◦ • W • ◦ • ◦

• ◦ • ◦ • ◦ •

6 black and 6 white queens on a 7 x 7 board:

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

B ◦ • ◦ B ◦ •

◦ • W • ◦ • W

• ◦ • ◦ • ◦ •

7 black and 7 white queens on a 7 x 7 board:

• B • ◦ • B •

◦ B ◦ • B • ◦

• B • ◦ • B •

◦ • ◦ • B • ◦

W ◦ W ◦ • ◦ W

◦ • ◦ W ◦ • ◦

W ◦ W W • ◦ •

</pre>