[Jprogramming] sparse scatter-modify

[David Lambert]

matrix representation of a graph failure
( https://adventofcode.com/2019/day/6 )

   JVERSION
Engine: j901/j64avx2/windows
Release-c: commercial/2020-01-11T13:29:14
Library: 9.01.22
Platform: Win 64
Installer: J901 install
InstallPath: c:/program files/j901
Contact: www.jsoftware.com

   I=:_2]\0 1 2 3 4 5 6 7 1 0 3 2 5 4 7 6

   1 I } 8 8 $ 0
0 1 0 0 0 0 0 0
1 0 0 0 0 0 0 0
0 0 0 1 0 0 0 0
0 0 1 0 0 0 0 0
0 0 0 0 0 1 0 0
0 0 0 0 1 0 0 0
0 0 0 0 0 0 0 1
0 0 0 0 0 0 1 0

   1 I } 1 $. 8 8 ; 0 1 ; 0
0 0 | 1
0 1 | 1
0 2 | 1
(snip)
7 3 | 1
7 4 | 1
7 5 | 1
7 6 | 1
7 7 | 1

Stay well!  Dave