I have an array such as A-B-C-D-E-F-G-H-I-J-K I want to rotate it N places to the right; for example, if N=3, the array should end I-J-K-A-B-C-D-E-F-G-H

Assume that the only available operation is a FLIP method that can invert any portion of the array. For example, applied to the original array FLIP(3,6) would produce A-B-F-E-D-C-G-H-I-J-K.

If the array is L elements long, you could do N times something like

FLIP(L-1, L)
FLIP(L-2, L-1)
FLIP(L-3, L-2)
...
FLIP(1,2)

and in a BASIC like language the code could be something like

FOR I=1 TO N
    FOR J=L-1 DOWNTO 1
         FLIP(J,J+1)
     NEXT J
NEXT I

but this seems too kludgy - I think there must be a better way.

Posted by Oskar on 2004-04-19 17:51:17