Solving Queens in J from a novice J programmer:

   randomboard =: 3 : '? (y,y) $ y'
   testsolution =: 4 : 0
   m =. x
   n =. #x
   n -: # ~. ({&m) <"1 (i. n) ,. y A. (i. n)
   )
   findsolution =:3 : 0
   board =: y
   ns =. 1 i.~ (board & testsolution)"0 i. !#y
   if. (ns = !#y) do. 'No solution found' else. ns A. i. #y end.
   )
     
   writesolution =: 4 : 0
   board =. x
   sol =.y
   m1 =. m
   n1 =. #x
   count =. 0
   for_a. sol do.
     m1 =. n1 (< count , a) } m1
     count =. count + 1
   end.
   m1
   )
   
   writewithsolution=: 4 : 0
   m1 =: x writesolution y
   (":"1 x) ,. '|' ,. ":"1 m1
   )
   
   m =: randomboard 9
   echo m writewithsolution findsolution m

      load 'queens.ijs'
   5 2 8 0 3 3 0 5 2|9 2 8 0 3 3 0 5 2
   8 2 3 6 7 7 4 5 1|8 9 3 6 7 7 4 5 1
   6 1 5 8 3 5 8 7 6|6 1 5 9 3 5 8 7 6
   8 4 8 8 7 5 1 1 1|8 4 8 8 9 5 1 1 1
   2 6 7 6 5 4 7 3 1|2 6 7 6 5 4 7 9 1
   6 8 1 4 1 4 3 2 7|6 8 1 4 1 9 3 2 7
   6 0 5 6 5 5 8 5 0|6 0 5 6 5 5 8 5 9
   1 7 5 5 8 1 1 0 1|1 7 5 5 8 1 9 0 1
   8 4 6 2 2 4 6 4 1|8 4 9 2 2 4 6 4 1