USING: accessors alien.c-types classes.struct combinators
hash-sets hashtables kernel locals math math.parser sequences
sets specialized-vectors vectors ;
IN: ant

! TUPLE: point { x uint } { y uint } ;
! : <point> ( x y -- point ) point boa ; inline

STRUCT: point { x uint } { y uint } ;
: <point> ( x y -- point ) point <struct-boa> ; inline

: push-point ( x y stack -- )
    [ <point> ] dip push ; inline
: >point< ( point -- x y ) [ x>> ] [ y>> ] bi ; inline

: sum-digits ( n -- x )
    0 swap [ dup zero? ] [ 10 /mod swap [ + ] dip ] until drop ; inline

: walkable? ( point -- ? )
    [ x>> ] [ y>> ] bi [ sum-digits ] bi@ + 25 <= ; inline

:: ant ( -- total )
    HS{ } clone :> seen
    200,000 <vector> :> stack

    1000 1000 <point> stack push

    0 [ stack empty? ] [| total |
        stack pop :> p
        p seen in? [ total ] [
            p seen adjoin
            p walkable? [
                p >point< stack {
                    [ [ 1 + ] 2dip push-point ]
                    [ [ 1 - ] 2dip push-point ]
                    [ [ 1 + ] dip  push-point ]
                    [ [ 1 - ] dip  push-point ]
                } 3cleave
                total 1 +
            ] [ total ] if
        ] if
    ] until ;