From 02a84743ddf5c8c27a36c4d5a20eaf3cd2a9aff4 Mon Sep 17 00:00:00 2001
From: Shinya Sato <shinnya.sato@gmail.com>
Date: Sun, 28 Aug 2022 20:40:57 +0900
Subject: Update for n-queens

---
 comparison/OCaml/nqueen12.ml | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 comparison/OCaml/nqueen12.ml

(limited to 'comparison/OCaml/nqueen12.ml')

diff --git a/comparison/OCaml/nqueen12.ml b/comparison/OCaml/nqueen12.ml
new file mode 100644
index 0000000..fc56542
--- /dev/null
+++ b/comparison/OCaml/nqueen12.ml
@@ -0,0 +1,23 @@
+let rec member x alist =
+  match alist with
+    []    -> false
+  | y::ys -> if x=y then true else (member x ys);;
+
+let rec threat k m alist =
+  match alist with
+    []    -> false
+  | x::xs ->  if (k = x-m) || (k = m-x) then true
+              else (threat (k+1) m xs);;
+
+let rec queen1 m b n =
+  match m with
+    0 -> []
+  | m ->
+    if (member m b) || (threat 1 m b) then (queen1 (m-1) b n)
+    else if (List.length b) = (n-1) then [m::b]@(queen1 (m-1) b n)
+         else (queen1 n (m::b) n) @ (queen1 (m-1) b n);;
+
+let queen n = queen1 n [] n;;
+
+let n = 12;;
+let () = print_int (List.length (queen n));
-- 
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