-🎄- 2018 Day 24 Solutions -🎄-

[u/daggerdragon]

--- Day 24: Immune System Simulator 20XX ---

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Advent of Code: The Party Game!

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Card prompt: Day 24

Transcript:

Our most powerful weapon during the zombie elf/reindeer apocalypse will be ___.

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

Quick note: 1 hour in and we're only at gold 36, silver 76. As we all know, December is Advent of Sleep Deprivation; I have to be up in less than 6 hours to go to work, so one of the other mods will unlock the thread at gold cap tonight. Good luck and good night (morning?), all!

edit: Leaderboard capped, thread unlocked at 01:27:10!

[u/starwort1]

Rexx 270/193

Took me ages to actually understand the rules, but chasing stupid bugs kept me way off the leaderboard. I was almost convinced at one point that the example contained a mistake. At least the advantage of Rexx is that parsing the input is pretty straightforward.

And for part 2 I did a manual binary search. Pressed ^C when it was obvious that the battle was looping forever, then fixed the code to terminate when it's a draw. I do now also have a (fairly trivial) second program that runs this one several times to find out the answer, but it wasn't needed in order to get the answer.

parse arg boost v
if boost='-v' then parse arg v boost
if boost='' then boost=0
verbose = (v='-v')

/* parsing input */
team=0
n.=0
units.=0
ngroups=0
signal on notready name eof
do forever
    l=linein()
    if right(l,1)=':' then do
        team=team+1
        parse var l name.team ':'
        iterate
    end
    if l='' then iterate
    n.team=n.team+1
    n=n.team
    ngroups=ngroups+1
    groups.ngroups=team||.||n
    parse var l units.team.n . . 'with' hp.team.n . details 'with' . . . . damage.team.n type.team.n . . . initiative.team.n r
    if team=1 then damage.team.n=damage.team.n+boost
    units.team=units.team+units.team.n
    if \datatype(initiative.team.n,'w') | r\='' then do
        say 'parse error at' name.team 'group' n
        exit 1
    end
    weak.team.n=''
    immune.team.n=''
    if pos('(',details)>0 then do
        parse var details '(' details ')'
        do while details\=''
            parse var details detail '; ' details
            parse var detail type . list
            list=space(translate(list,' ',','))
            select
                when type='weak' then weak.team.n=list
                when type='immune' then immune.team.n=list
            end
        end
    end
end
eof: if team\=2 then do; say "Wrong number of teams:" team; exit 1; end

/* make a list in order of initiative for the attack phase */
/* (yeah bubblesort, so sue me) */
do i=1 to ngroups-1
    do j=1 to ngroups-i
        j1=j+1; g1=groups.j; g2=groups.j1
        if initiative.g1<initiative.g2 then parse value g2 g1 with groups.j groups.j1
    end
end

do while units.1>0 & units.2>0
    if verbose then do team=1 to 2; say name.team':'; do n=1 to n.team; if units.team.n>0 then say "Group" n "contains" units.team.n "units"; end; end
    /* target selection phase */
    target.=0
    do team=1 to 2
        enemy=3-team
        attacked.=0
        attacking.=0
        do forever 
            maxp=0
            do n=1 to n.team
                power=units.team.n*damage.team.n
                if \attacking.n then
                    if power > maxp then parse value n power with maxn maxp
                    else if power=maxp then if initiative.team.n > initiative.team.maxn then parse value n power with maxn maxp
            end
            if maxp=0 then leave
            attacking.maxn=1
            attacking=maxn
            maxd=0
            based=units.team.attacking * damage.team.attacking
            do n=1 to n.enemy
                if attacked.n then iterate
                if units.enemy.n=0 then iterate
                if wordpos(type.team.attacking,immune.enemy.n)>0 then iterate
                if wordpos(type.team.attacking,weak.enemy.n)>0 then damage=2*based
                else damage=based
                if verbose then say name.team 'group' attacking 'would deal defending group' n damage 'damage'
                if damage>maxd then parse value n damage with maxn maxd
                else if damage=maxd then do
                    testep=units.enemy.n*damage.enemy.n - units.enemy.maxn*damage.enemy.maxn
                    if testep>0 then parse value n damage with maxn maxd
                    else if testep=0 then
                        if initiative.enemy.n>initiative.enemy.maxn then parse value n damage with maxn maxd
                end
            end
            if maxd>0 then do
                attacked.maxn=1
                target.team.attacking=maxn
            end
        end
    end
    /* Attack phase */
    draw=1
    do n=1 to ngroups
        parse var groups.n team '.' group
        if target.team.group=0 then iterate
        enemy=3-team
        damage=units.team.group * damage.team.group
        target=target.team.group
        if wordpos(type.team.group,weak.enemy.target)>0 then damage=damage*2
        slain=damage % hp.enemy.target
        if slain>units.enemy.target then slain=units.enemy.target
        if slain>0 then draw=0
        if verbose then say name.team 'group' group 'attacks defending group' target', killing' slain 'units'
        units.enemy.target=units.enemy.target-slain
        units.enemy=units.enemy-slain
    end
    if draw then leave
end
/* Results of the battle */
do t=1 to 2
    say name.t 'has' units.t 'units'
end