User:Oleg Kobchenko/PermRevLexRank

• OEIS:A056019 - Self-inverse infinite permutation which shows the position of each finite permutation's inverse permutation in OEIS:A055089
• JForum:programming/2007-September/008062 inverse permutation vector

pr=: 3 : 0   NB. PermRevLexRank - unfinished sketch
  r=. - {.y
  for_j.>:i.-<:#y do.
    r=. r + (j - j{y) * !x:j
    y=. ( (j{y) (]-<) (j-1){.y ) , j}.y
  end.
  r
)

   Ai=: A.@/:@(A. i.)~"0
   4 Ai i.!4
0 1 2 4 3 5 6 7 12 18 13 19 8 10 14 20 16 22 9 11 15 21 17 23

viewmat |:(5 Ai i.!5) A. i.5

   ,.|:&.> (2 3 4 #: i.!4) ; (4 3 2 1 #: i.!4) ; (4 Ai i.!4) A. i.4
+-----------------------------------------------+
|0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1|
|0 0 0 0 1 1 1 1 2 2 2 2 0 0 0 0 1 1 1 1 2 2 2 2|
|0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3|
+-----------------------------------------------+
|0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3|
|0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2|
|0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1|
|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|
+-----------------------------------------------+
|0 0 0 0 0 0 1 1 2 3 2 3 1 1 2 3 2 3 1 1 2 3 2 3|
|1 1 2 3 2 3 0 0 0 0 0 0 2 3 1 1 3 2 2 3 1 1 3 2|
|2 3 1 1 3 2 2 3 1 1 3 2 0 0 0 0 0 0 3 2 3 2 1 1|
|3 2 3 2 1 1 3 2 3 2 1 1 3 2 3 2 1 1 0 0 0 0 0 0|
+-----------------------------------------------+

 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 (]+<:) 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2
 1 1 2 2 3 3 0 0 2 2 3 3 0 0 1 1 3 3 0 0 1 1 2 2

 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2 (]+<:) 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 (]+<:) 1 2 0 2 0 1 1 2 0 2 0 1 1 2 0 2 0 1 1 2 0 2 0 1
 2 3 1 3 1 2 2 3 0 3 0 2 1 3 0 3 0 1 1 2 0 2 0 1

 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 (]+<:) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2 0 0 1 1 2 2 (]+<:) 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 (]+<:) 2 1 2 0 1 0 2 1 2 0 1 0 2 1 2 0 1 0 2 1 2 0 1 0
 3 2 3 1 2 1 3 2 3 0 2 0 3 1 3 0 1 0 2 1 2 0 1 0

   7 8 A. 'abcd'
badc
bcad
   7 8 ((] + <:)/\"1@(#:~ (- i.)@#) { ]) 'abcd'
badc
bcad