Advent of Code 2018

day9.ijs

left =: 4 : 0
  if. y = 0 do. x - 1
  else. <: y
  end.
)

right =: 4 : 0
  if. y = x do. 1
  else. >:y  
  end.
)

nsum =: 3 : '(y * >: y) % 2'

play =: 4 : 0
  scores =: 0 * i. x
  marbles =: 0
  n =: 1
  p =: 0
  while. n <: y do.
    nm =. # marbles
    if. 0 = 23 | n do.
      si =. x | n
      pi =. nm | p - 7
      np =. n + pi { marbles
      scores =. (si {. scores) , (np + si { scores), ((>:si) }. scores)
      marbles =. (pi ~: i. nm) # marbles
      if. pi = # marbles do. p =. 0
      else. p =. pi
      end.
    else.
      p =. nm right nm right p
      marbles =. (p {. marbles) , n , (p }. marbles)
    end.

    if. (nsum n) ~: (+/ marbles) + (+/ scores) do.
      echo 'oh no' ; n ;(nsum n) ;(+/ marbles) ;(+/ scores)
    end.

    NB. echo marbles ,: p = i. (# marbles)
    n =. >: n  
  end.
  echo 'marbles'; +/ marbles
  echo 'scores'; scores
  echo >./ scores
  scores
)

play2 =: 4 : 0
  scores =: 0 * i. x
  lefts =: (>: y) $ _999
  rights =: (>: y) $ _999

  lefts =: 0 (0}) lefts
  rights =: 0 (0}) rights

  n =: 1
  p =: 0

  while. n <: y do.
    if. 0 = 23 | n do.
      p =. ({ & lefts)^:7 p
      si =. x | n
      np =. n + p + si { scores

      scores =. np si} scores

      NB. echo scores

      oldr =. p { rights
      oldl =. p { lefts
      NB. echo p
NB. echo 'eh'; lefts ,: rights
      lefts =. (_999 , oldl) (p , oldr)} lefts
      rights =. (_999 , oldr) (p , oldl)} rights
      p =. oldr

NB. 1echo 'oh';< lefts ,: rights
    else.
      p =. (p { rights)
      oldr =. (p { rights)

      rights =.  (oldr , n) (n , p)} rights
      lefts =. (p , n) (n , oldr)} lefts
      p =. n
    end.


NB.      inplay =. +/ (lefts ~: _999) *. i. >: y
NB.      if. (nsum n) ~: (inplay + +/scores) do.
NB.         echo 'oh no' ; n ; inplay ; scores
NB.      end.

 
    NB. echo < lefts ,: rights

    n =. >: n
  end.
  >./scores
)