Looks pretty standard. It starts by placing one queen on each square of the bottom row, then working up through the rows trying to put a queen in each column. If it can place a queen it gets added as a possible solution. The always test in the inner loop checks the 'rook' horizontal and then the 'bishop' diagonal. The bishop test is a bit tricky, it looks at (x rows up, y columns across from a previously placed queen) If x and y are equal it's on the diagonal.
-- Geoffrey Summerhayes On Sunday, July 8, 2012 8:00:54 PM UTC-4, Victor Manuel Grijalva Altamirano wrote: > > > The next solve the problem of eight Queeen... but i don't undestand > it!!!.... can you explain me? > > (defun n-queens (n m) > ( > > if (= n 1) > (loop for x from 1 to m collect (list x)) > > > (loop for sol in (n-queens (1- n) m) nconc > (loop for col from 1 to m when > (loop for row from 0 to (length sol) for c in sol > always (and (/= col c) > (/= (abs (- c col)) (1+ row))) > finally (return (cons col sol)) > ) > collect it > ) > ) > ) > ) > > > > > -- > Victor Manuel Grijalva Altamirano > Universidad Tecnologica de La Mixteca > -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To view this discussion on the web visit https://groups.google.com/d/msg/algogeeks/-/qv0m-4stZdEJ. To post to this group, send email to algogeeks@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
