You have three small poles and five hoops - XS, S, M, L, XL (as in extra small, small, medium, large and extra large). They are placed on pole 1 in order, with largest at the bottom.

You can move one hoop at a time, and the hoops you are not moving have to be on a pole. You also cannot place a hoop on top of a smaller one. How can you move the hoops so that they are in the same order as they are now, but on pole 3?

(In reply to Recursion challenge by Gamer)

DECLARE SUB transfer (n!, source!, dest!)
INPUT "Number of hoops:", n
transfer n, 1, 3

SUB transfer (n, source, dest)
  IF n = 1 THEN
    PRINT "Move A from"; source; "to"; dest
  ELSE
    transfer n - 1, source, 6 - source - dest
    PRINT "Move "; CHR$(ASC("A") + n - 1); " from"; source; "to"; dest
    transfer n - 1, 6 - source - dest, dest
  END IF
END SUB

with sample runs:
Number of hoops:3
Move A from 1 to 3
Move B from 1 to 2
Move A from 3 to 2
Move C from 1 to 3
Move A from 2 to 1
Move B from 2 to 3
Move A from 1 to 3

Number of hoops:4
Move A from 1 to 2
Move B from 1 to 3
Move A from 2 to 3
Move C from 1 to 2
Move A from 3 to 1
Move B from 3 to 2
Move A from 1 to 2
Move D from 1 to 3
Move A from 2 to 3
Move B from 2 to 1
Move A from 3 to 1
Move C from 2 to 3
Move A from 1 to 2
Move B from 1 to 3
Move A from 2 to 3

Posted by Charlie on 2003-09-07 16:12:32