Data commit

Task/N-queens-problem/Nim/n-queens-problem.nim

@@ -0,0 +1,29 @@
+const BoardSize = 8
+
+proc underAttack(col: int; queens: seq[int]): bool =
+  if col in queens: return true
+  for i, x in queens:
+    if abs(col - x) == queens.len - i:
+      return true
+  return false
+
+proc solve(n: int): seq[seq[int]] =
+  result = newSeq[seq[int]]()
+  result.add(@[])
+  var newSolutions = newSeq[seq[int]]()
+  for row in 1..n:
+    for solution in result:
+      for i in 1..BoardSize:
+        if not underAttack(i, solution):
+          newSolutions.add(solution & i)
+    swap result, newSolutions
+    newSolutions.setLen(0)
+
+echo "Solutions for a chessboard of size ", BoardSize, 'x', BoardSize
+echo ""
+
+for i, answer in solve(BoardSize):
+  for row, col in answer:
+    if row > 0: stdout.write ' '
+    stdout.write chr(ord('a') + row), col
+  stdout.write if i mod 4 == 3: "\n" else: "      "