Solve hanging lantern problem: Difference between revisions

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 Examples of this approach are left as an exercise for the user.
+Finally, enumerating solutions might be approached recursively:
+<lang J>showlanterns=: {{
+  arrange=. ($ $ (* +/\)@,) y $&>1
+  echo 'lantern ids:'
+  echo rplc&(' 0';'  ')"1 ' ',.":|:arrange
+  echo ''
+  cols=. <@-.&0"1 arrange
+  recur=: <@{{
+    todo=. (#~ ~:&a:) y -.L:0 x
+    if. #todo do.
+      next=. {:@> todo
+      ,x <@,S:0 every next recur todo
+    else.
+      <x
+    end.
+  }}"0 1
+  echo 'all lantern removal sequences:'
+  echo >a:-.~ -.&0 each;0 recur cols
+}}</lang>
+Example use:
+<lang J>   showlanterns 1 2 1
+lantern ids:
+2 4
+all lantern removal sequences:
+3 2 4
+3 4 2
+4 3 2
+1 2 4
+1 4 2
+2 1 4
+2 4 1
+4 1 2
+4 2 1
+1 3 2
+3 1 2
+3 2 1</lang>
 =={{header|Julia}}==