rajcode -- finds the Rajchgot code of a permutation

Description

Given a permutation in 1-line notation, finds its Rajchgot code, as defined in [PSW].

[PWS]: O. Pechenik, A. Weigandt, and D. Speyer, "Castlenuovo--Mumford regularity of matrix Schubert varieties" (see arXiv:2111.10681).

i1 : w = {7,2,5,8,1,3,6,4}

o1 = {7, 2, 5, 8, 1, 3, 6, 4}

o1 : List

i2 : rajcode w

o2 = {6, 4, 4, 4, 1, 1, 1, 0}

o2 : List

i3 : v = {1,6,9,2,4,7,3,5,8}

o3 = {1, 6, 9, 2, 4, 7, 3, 5, 8}

o3 : List

i4 : rajcode v

o4 = {4, 5, 6, 2, 2, 2, 0, 0, 0}

o4 : List

The source of this document is in MatrixSchubert/permutationMethodsDOC.m2:402:0.