day_11_complete.ijs

seats =:  (90 91 $ ;'L' = &> ;(LF cut fread '~/code/advent_of_code/day_11.txt'))
is =: dyad : '+/ ;x = ;y'
pad =: monad : '|:0,|: 0,  y'
unpad =: monad : '(<:$ y) $ (0 0 ,: <:$ y) ,;.0 y'
tile =: monad : ';"2 (1 1,: 3 3) ];.3  y'
count =: dyad : '(x is &> <"1 y)'
step =: monad define
  occupied =. unpad 2 count tile pad y
  comingAlive =. (y = 1) * (0 = occupied)
  dying =. (y = 2) * (4 < occupied)
  stayingAlive =. (y = 2) * (4 >: occupied)
  dying + (comingAlive +. stayingAlive) * 2
)
s =: seats
ex =: monad define
  s =: step s
  +/ ;2 = s
)
}. ,.ex &> i.100 NB. just do it a bunch of times until it stops changing