Update for n-queens

1 files changed, 21 insertions, 0 deletions

diff --git a/comparison/Haskell/nqueen-12.hs b/comparison/Haskell/nqueen-12.hs
new file mode 100644
index 0000000..1efb57b
--- /dev/null
+++ b/comparison/Haskell/nqueen-12.hs
@@ -0,0 +1,21 @@
+member x [] = False
+member x (y:ys)
+  | x==y = True
+  | otherwise = member x ys
+
+threat k m [] = False
+threat k m (x:xs)
+  | (k == x-m) || (k == m-x) = True
+  | otherwise = threat (k+1) m xs
+
+
+queen1 0 b n = []
+queen1 m b n
+  | (member m b) || (threat 1 m b) = (queen1 (m-1) b n)
+  | (length b) == (n-1) = [m:b] ++ (queen1 (m-1) b n)
+  | otherwise = (queen1 n (m:b) n) ++ (queen1 (m-1) b n)
+
+queen n = queen1 n [] n
+
+n=12
+main = print $ (length (queen n))