AoC 2021 day 6 (dc)

[q] SX

[
    z 0 =X                  # stop when stack empty
    d;g 1+ r:g              # g(top) = g(top) + 1
    lLx                     # loop
] SL
lLx

[
    1- d _1=X               # i = i-1 -> (i == _1 exit) i
    d lt+;g ls+ ss          # i -> (s = s + g(t+i)) i
    lSx
] SS

[
    0 ss 9lSx s.
    [Part 1: ]n lsps.
] S1

[
    lt d 80=1 d 256=X
    d;g r7+ ;g+ lt7+:g      # t -> g(t) t -> g(t+7)+g(t) -> g(t+7) = g(t+7)+g(t)
    lt d;g r9+ ;g+ lt9+:g   # ditto, but with t+9
    lt 1+ st                # t++
    lTx
] ST
0 st lTx

0 ss 9lSx
[Part 2: ]n lsps.