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

@@ -0,0 +1,25 @@
+const boardSize = 8
+
+proc underAttack(col, queens): 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): auto =
+  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)
+
+for answer in solve(boardSize):
+  for i, x in answer:
+    if i > 0: stdout.write ", "
+    stdout.write "(",i,", ",x,")"