day 17, part 2

day17-hard/build.zig

@@ -0,0 +1,70 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard optimization options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+    // set a preferred release mode, allowing the user to decide how to optimize.
+    const optimize = b.standardOptimizeOption(.{});
+
+    const exe = b.addExecutable(.{
+        .name = "day17-hard",
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = .{ .path = "src/main.zig" },
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
+    const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
+    run_cmd.step.dependOn(b.getInstallStep());
+
+    // This allows the user to pass arguments to the application in the build
+    // command itself, like this: `zig build run -- arg1 arg2 etc`
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const unit_tests = b.addTest(.{
+        .root_source_file = .{ .path = "src/main.zig" },
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const run_unit_tests = b.addRunArtifact(unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_unit_tests.step);
+}

day17-hard/hard.in

@@ -0,0 +1,141 @@
+222122122231132231322211344413343224131243444121251443112234151542155511322545515353242232442232122121113322132431241211221323312223212221121
+221212212121132323222322221441212241211143123341542312443541441234253155552535351521123434324424112444312231142314323423333123222232322121212
+112123212233331112123312314221334241332121421445511221433331444342123424512243235222323232332214423133232333134131224411112332133111112322222
+122112222212212132323131242113444331433142445424221251521555235313532112313322255134553552115315313113243412233442311143122123223213133222322
+121313323133211312321442111122342222424533324321412433351321412345435313521524255245334452224535431325224424132131433122113421123223322311312
+223322322113231323323121431311331442323325322143542121151325423243135154124441223123155211514115544224224533122432441422331233213213211112333
+211221333111231334442233213313212124115241213343454552345314425543233451244541113145233332551551121222453145312111413413443113322222213231321
+123311112122231441124143331243431411534132154525553531252355411333225115522455524445413424142111522433415132123423211111323311313113121231233
+322111112133321334412334314241211332332422125351345425423241534445446644362435542243452125422432123525432131353431343334422142121333313331233
+233211232323244144111142443214334334225331424324315412423655324625464225645225446224264513323334243452123134343154223113143324242113323123313
+231123211133314114321433243123453221334333341441132142235552352664454363455625644464636355113312211542322431555315234133432213313113212111323
+322231111311122134234331434525352421131241251443436635363264522235224325354443323522665466432342414322225322411415333244143412424112323321321
+233121113341412342331434214555411115225323135453463244323466652642665434364266544342443433434564424514332533354543241211421322413333221123232
+311131333233343324413424153323423345332242452565235662565663542524466536625224526262524624243565535253123511544432244121434324331124422211132
+122213133134314141322123243244335453335224456653226324263455333252343355243646225335622653352266644552344553545155152144214314143313312113213
+232311331231441124232413325415351221421424542236466444346645423332345642453356546255255534523644555255234141235541125144434344222121212111231
+323323212141143212223253242543455511144543333522666354523243426343544622622335456222525264352455366533321354135554533153334321211424144422231
+333111323344114441243414324425531413542626426526444523253254545343656655322645254625623544246365264223355552353144515344531112113413424431331
+231132344212442123351153414143113255223464232642634333545545466642533635554365353252353642366255342545634642331522355325314242332444344424312
+213234222433433231333222232355323332462646662456525466542353637457336556766575474556252626646262625523353652113132424511555234124113123423413
+232244322434331132311455332234251324564365335623223442646537665345454677376667537347544252333654532533342252631322251552241354433123422122231
+312114121134133442432314431145236635222643442556655643547466346537335363645633375743545647554364643326322443363541134232124312524314113432313
+113133413314323345412414354435446633262236345636624764744374547733536753443633745357344765443545344643242525363341212221532554514432312412422
+121341114244342531442555522144652356644324256322477437765734635435435657346767657336465566756564552336243532442625553323432344222141212234122
+323331332132215445234524223336654356565632454234645675454545644567457765447477766434777735444736666645443245633532213211243125231321212121222
+431242423432224422425152415342454325346345643333667766543746476463453573473553577633365757643767754326656542442444231142135431321331423431311
+414422414421443352213413216453433544624563244747675366653673453455637577536657367376654447437777473725633325253242434113325125241221234321442
+242312341232332541411233342324526442252543334546763337353554644476333653647465333554633446645743363534225555622646632331553242521431324323314
+341341311315443125523533535655464536255655765756445545457465775466756337467674675544754344466775555555322325244364554461451522115535331444313
+311444421242232535232543566462654535446555447575436754664366755378774578855758543436463465435767465436566534633233655452534141325434434332223
+341132443324155244522354642365632653556373633763467535566653475885475474685486557455477563575664464653366333556626336622351544334233252231224
+431344122531333525141422424664465256435374554563565374755757657855685856457576688768575335476567357737355643362652222423452154221351323413121
+232442322115534513553226545526236635776453767365563456587645655857668464487555677754868566754576577764637574363362555554463133323343251223213
+242423441314215242212254666632655654647544767767665345676744878455547584466575858744855874675757443553363377322466363433245225455222444441143
+321141243421353544154442523556255334545353474354354565858848856486755487556444884647455885473463335765344476346665252262344522522332531532244
+221343423231531241353245434425637453355346534643586845685644485487765558875466556874546665646656576777674463463626652323526344343514324531224
+322112455343245245662543426345546453447335453758858546684788878866474787775866665776676855746784357436546435645762663462265445441432332143122
+411135144511455525543223656645435753747563437786477448454457787876754768755666457664456858776456475754677374675364543435556532143413445231343
+431213424253515326266624236442565654763763637886675856865686864588677556675748567585578754757685657465674574573645536663422466352545254245334
+342411222453551556535633655655643475737344557668666556846788686564746455567667746746676478864487665743533477344773666262244534345544133453212
+313233435523244224224224224457565435764733787845577566456887775678987776797855566778588587578675746643444434455343422225566455444553321313143
+113412524114122623622546522675376537754356785565487477864745788559788586968757786878655585747654787544337446535535345655325245631121152534351
+333423224144335462322242456634775675775466865685888455647696985599766868557797768757957545847585668477476555565743465622323654265224221113414
+323223322231256466254463563674667755667465444457764655545999567659965579658779867755676846745556666655767373767436676243366263252431145144244
+144454412235442445532326654654473757557655487548675774686985975967586996555656956568697685767765476664743436574557535654226654554552425413553
+222222112245252223532344463573455655745555878466657545758575687776999867858597867868767855464784686754577747546434573663662322263235332511412
+135253144321522556463664545543434773376544465757845558798669956959696577568655897787679576864665545777585577434536475655223265436355523541453
+245134515145562655323535663476734667867884856685475797758586968688657659657766757775657856969465857777576845476736646555424464262243223424411
+325251343131336545335233634756567345656464664487566658685756588678576877778878558798569557767687488655487654745736453465445642226333343232325
+215145425525636535544555774546333357445567586844869688788667975778656855679557956788788868889685754746886647333367476673535456554634314554545
+211544421215625434644423576546464468767548584446979866788985569668798767877988599669676975557587785677878746445654364357544556224264422451424
+215334112242254254255237434647573364574547556887985699889956887968877879877899677989757685555569766585848776666355534576352532232466445113154
+321415512242235422652654466456533564477856466498778555668667976967999779989869886756789996979857645477788848587437536565655432365255323421523
+133142513525422364643655574747664864567874644777775775979879867796778887888696986689786696656575797885678556845554377345554334643264525543445
+142555214134363424562747533634657884744488786556975596759557767889797678789688799678999789558598657788485556564634773344344655623524412112144
+242131121452542363553433474344666488757567657968659857886677686697768777866769777988679799889687568446685586677443645564654323666545215444335
+335534251235355465626343634453776464886844685989658757998768886979679986776787678879896989786988959655867645454534346565775223344264443232412
+211412213632436324563636774777565788785567788999866656589696996699669896776798968879976969585957876654666747547644443774345426553645654414432
+131212555236333224233556664365456747864547576799788888899978689689966978889779986687997795878787686675478887484677356565335466522433642233421
+132555242335655624566773335547668764775754597599757859986996988689886786999679977889767776768679966867674668545453333436675632364235552555225
+543345554323425566277565775665677774588445899885889678677767679699698699786877768698889779969865599865455676567774333453546545325363465241153
+454315546552224634567466554455468787487467677878676599867977888696698889999989777776976778857995865995778645565583557535534454322666334443223
+344434333654356353646733364467866877477868886679769789797997776889897887887798697689776997957859788655556856477476446736547545646325653211524
+412325525232545264257647537337744575447875695879575868969886769677978877987998867987666866896586685666456655856555765556355555623263532545525
+213322543424652533234344353577647648644699869755765997768989689799797979989988989676967968685866767867667686848557774647574353236565445514535
+431223153622644655663364556534566485867588559795955969769899769877978898998998778696669997888787865695666648674684477336534533242223243543123
+331325156532322624267346777358454567758478665799855668877787968998987898789977899977799667866757659575665465647765534576373664454445554452244
+434244324534323244667474775445568788564785675958675699779767977898899988979898779768896976668976598795948655588644776646345435266334433423121
+411232445234266435556455576454578576464766868586997899868677787999799988978987878878687666887776768769568667846784536664343465623635642224352
+113545245462445532357533764338457885767798969868689789768779779877898989988788999777986677677557759888987456886468644457653543366355655433244
+453132215426636344446354376478646464757566966989878966888777688778999779897887997999687896968767959887886565485465567464763333562665654244234
+334442534553425264556336675764447446568897998855957968797669787787988789797978899867698889999889757676755565486758744755544563666264662223333
+154123456625353626446467377666845574758876977886667899687798677988789987997788989997799897676595568766855655688764657735443435254424224125333
+111452122256632622533454665767486748878885899765988667886879798998998889899878889887976679998875885968858847754457535354553465435553523242445
+524454154564524426474757764744478478566487565575579998876766999879797899789878979779678979966986956768968564586565553667456372465452426551424
+454321552243556433745466563555855654867585979559888869689697699798789787797999788769898779867587859668746644665467334565476766622644362111455
+113513156335233644354475637437786466656466766555975869878969678799889987989889899696668887796897665697674566588884573757345744263236662351155
+534141434433454622664663637557877678668458969695669686778766768779989998979898889668866979875995668896865865876465745335566465642465564235344
+424514223452466324667675544677676665884567878958695799966699686987888787978778987899767899976766989699844485668476366434634654233245256521245
+243131413263565235576657334546677484445487888675975687966986989679877999979878876898966798875656867566456544557575346675735544244462546534354
+452333545653543346534575657363757888858485886596596696677986967996787997988896788876766979879789688877876554788865376557667723636356356434315
+434231214245456235464536355743687845587887968785685777996866898889787778998767768887987669799977558785466746454563674537564456465246622544313
+535224144435335653533536333334855754466485786667599868867687677897876986969686777899796669659568575888546474654477455363373544465352461545553
+333222451255262433456533356637785864558574885576757776966679778978977667688689768678699979978895586656875657467564567746766262326662321111234
+354145242522363436243567443354586676746458969898899895767769869789676866768798889668688898587779897757464848467734434665653252254266225455244
+424533211322646256544734764557788486568545899865566877996897699697698777778869968686897699769997687774446874767456553434653465336233625335222
+431251444525363244345435335753357677588765675769756979678686768997689978767776798699897659868976759846556775877445545473454233554242341342454
+413434435334664425434474545754337446778585859577767967986879799867667897679986768779875858597865756684466745647435575444762342565424531512315
+245123553436255345635447377443653744457664744976787799656967887787877777876699968789798598557968697485466576484543453345735366632434411343552
+545545254546625532565377367365754757576844684786579995796965989766866879999778799768889577887588994775786555546475363547444525543456225331151
+511225125113346243455335377476664477867745486869567979586795878869877798779889777588688987585877787567558577644733644536454222356226244334223
+415225245113442552522654646475745466554558784688685866799587697669997668687667796996958967686675445476768868673444654435355554454244325441444
+142423555252362223524453353664456647455566454547686898695859786666766768866788885877569679896876477774856675377776776354633342444243313444254
+551525511245533525664436346466634648855747546886675595567799566987895595596858568956657757988677854487568864767737656567465662324645541253314
+322333152454643544635262636753467547587777788548555688967796678896878566897789878876775866989648848785745775745636736575325533555452211552554
+243253231351334356625553657333767546856444585674749879977775668567795656899989885769587558558788784458578654677777434565524266565333433543151
+124322232154236565345326256474456756445445648887684458886795956558878756666688865966868976585845454845664435437655634544462324556521412123213
+435153425521352635625365563737336443534556845844854687676866689559786795868887885857957686887845867768765563673356446764524224636611535222551
+321232444555136553346446255633576636675648865568774747666868556899959997969886767585865657448467454667575664643535336243225323252353222114123
+222232144315226533365254247366356533346678444588564868475699685565967775967779765976695478474557567586455764576335655635352244444114532352451
+244325224221353222655235322363666575674468755478868866585597966759896568585968898778886848578645846758437633453674332364542324535333434444423
+124424212312322353445233226475343535756668457785745786768488688955858689978999989558857677668548788787576355363346435233655442654341541222241
+421212512423132224623636654663756774656365547647578747847785668479667586795699966884677644687777488667676456575337454246642663314215521452442
+442214222241212134665264656453354654645474574488754466674785465844468747886767758868848587687568478457673777577755564363335334413341454411331
+331314454144121322334255365536755456777476736747665748457788784667844688666746684648878565668548876634536745767735635445246456423415341211421
+424333432123434115336233266566554336363463776756766658678748776847584754467848457575465585586858554333633775735345256543636634154352131421122
+233331424153545552352442352626444664444465757367686564666786544445784586887864555557857885458476557657563443577355626352223242535413511154434
+422342433424245224363656362243227455664455744456745547675485468556445447584755747568554847756843566376337467375436624642464431315212142332334
+442241354145524235544332652243546744447536465436654485684558877577547445748658684767857867477555556755343463456255542354544222113323512322224
+424111213243521532246263565442433335777346375463546545688587647868586885577575774448758847463546645537646536745636253663435445242343541413242
+144334425213415114225455553624443367363446537443543666388445776647447748866864676764844733675676746763743344622564253522432441535231421221214
+431321344512412321544365653545534625657533676457765445745646575844654875648555666886784776755737637647464476454666563455654123232421221314411
+122342424114251114312525352625262244445757753554735333674364744557875446745667785854476555473444356747433232335453465556451312125322224131424
+113132223314141241533526346455635366446574373754677674373367655336747564575786335373446375544455464666435553233435355332523245311343121111444
+332333112412255435325143343656235535566446637646766573535554363446433434746537536376443544644463534344646534266536424235324331145343214124113
+124122413211343423245421166456246553242243446643754653635646644467475557665673365634766734537533337632334632333355345543142143112444332132121
+444313143421325143515234233434232255555524657645367337457377566343675745756466757665453667774467546644242536644552355245532525342251413331441
+434312112411442132335453223553655662324246336345737345565775675677733644547476453653467374554754642342454422223645424133235444233241413312443
+113212423114112225114141322132664664534555243356374637363546554367556644334644456647563756463373464226663546425523344414332531245142411322111
+234444141443224442522134515435355435524553322246464436734477574335677773376455563333333665757754355324246643562243321433511453433322143121313
+214214123222212215153114332531522235526564244224346555756476744656353773355574735363674766655456553436243653623231533312424521514413131333244
+113141423334143121543212434133516456244563335325362444446363647446667574574436544643633333554445226543645323644352445432451525232133421241223
+111114313221431443243545121323351564424366523652526426225337343743544676573555746454645555666423463245546354225244251513215531332112424211422
+213113311231312132333132511153334535556233555345565445526642364743333475434573674742622225234444246554252256522443153342111134222324223241133
+122211344223331421153243235413313443252256344446654633245652254255575645667426666625325464332444355434466235525232534134424134414444444433123
+112211124221241344423555124441242315332564626264334623363554545342556252544623255262642455366625252623246233112131245151133112343113311222111
+133111221334141421214144242232144552335532552324444232243353243252526452254333364533433453553252644234445234435413425244451344411441314131221
+131213234444314423312125512332533242432136346556355236633654555546643565454426655422566542446423344233554143323311513424413423413133111421222
+121222312311133122233322532442435241545245232265542624524536662526244424224346236345644365265664425415152112542223245451222342414433121332211
+211333231411123241113131141223155141544345441335455322556534542335455354263622353536343466643356441412352535345232321341211133434144312132322
+322222112242223211333432321333114242141314213534622442554556526233234333635625234626466235625256332555542421541415145231424122443111313111221
+113121232122233134113431122233313415524144123324233323352453524552653345365526632522356642336455533512145355141435543243231411314444112113331
+131332132232321342232114341425511223245413414454524454532222534326352333332362336255646325221145452153244232153354114412221141231112122322333
+123332211322241431411143233142354322543555524212535411245626566452233624544655464643565522312225341154431415534511133434123112424233123311222
+231131312211322343443432211133213534151424125325143452444332426652443445466552643335411254544415443441514543424441234121321422322313323213223
+311221322232321221323411343233241451214322412152215542334151314124313244315144325515431155121521143324335343243231432433113414211221221213323
+231112211121312112331231411213441231225145115214415324135545114132323421241452531252423155152553453344553352442222241111314112113323321232313
+123232321112211223421311232412243213155523454531314113314534241323524512313223512212144555532423424211123331122231124212412123321321311121133
+112123123131331332321321321322332421134115124515412532313535253212112215121215331212325345523543544343351422412111222342233123312231133121332
+221123131333132322331422421334124233324442451431352341434451351322541333553224243113224314111333145521233421223113321342233313211232321333222
+222121333332331113312142331122114113111443345244442341124351355143153213151445415332443455532433335114344332141114234343122131212332121313211

day17-hard/sample1.in

@@ -0,0 +1,13 @@
+2413432311323
+3215453535623
+3255245654254
+3446585845452
+4546657867536
+1438598798454
+4457876987766
+3637877979653
+4654967986887
+4564679986453
+1224686865563
+2546548887735
+4322674655533

day17-hard/sample2.in

@@ -0,0 +1,5 @@
+111111111111
+999999999991
+999999999991
+999999999991
+999999999991

day17-hard/src/main.zig

@@ -0,0 +1,288 @@
+const std = @import("std");
+
+fn StackList(comptime T: type, comptime capacity_type: type, comptime capacity: capacity_type) type {
+    return struct {
+        const Self = @This();
+        mem: [capacity]T,
+        length: capacity_type,
+
+        fn add(self: *Self, value: T) void {
+            self.mem[self.length] = value;
+            self.length += 1;
+        }
+
+        fn addIfNotNull(self: *Self, nullable_value: ?T) void {
+            if (nullable_value) |value| {
+                self.add(value);
+            }
+        }
+
+        fn has(self: *Self, needle: T) bool {
+            for (0..self.length) |i| {
+                if (self.mem[i] == needle) {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        fn getMutableSlice(self: *Self) []T {
+            return (&self.mem)[0..self.length];
+        }
+
+        fn getSlice(self: *const Self) []const T {
+            return self.mem[0..self.length];
+        }
+
+        fn init() Self {
+            return Self{
+                .mem = undefined,
+                .length = 0,
+            };
+        }
+    };
+}
+
+fn RingQueueWrapper(comptime T: type) type {
+    return struct {
+        const Self = @This();
+        mem: *[]T,
+        first: usize,
+        next: usize,
+
+        fn add(self: *Self, value: T) void {
+            std.debug.assert(self.next - self.first < self.mem.*.len);
+            self.mem.*[self.next % self.mem.*.len] = value;
+            self.next += 1;
+        }
+
+        fn take(self: *Self) T {
+            const result = self.mem.*[self.first % self.mem.*.len];
+            self.first += 1;
+            return result;
+        }
+
+        fn isEmpty(self: *const Self) bool {
+            return self.next == self.first;
+        }
+
+        fn init(mem: *[]T) Self {
+            return Self{
+                .mem = mem,
+                .first = 0,
+                .next = 0,
+            };
+        }
+    };
+}
+
+const Direction = enum(u8) {
+    Horizontal,
+    Vertical,
+};
+
+const ResultsByDirection = std.EnumArray(Direction, u32);
+const Results = [150][150]ResultsByDirection;
+
+const Task = packed struct(u48) {
+    current_heat: u16,
+    x: u8,
+    y: u8,
+    entry_direction: Direction,
+    _: u8 = 0,
+};
+
+const NextTasks = StackList(Task, usize, 14);
+
+fn getNextTasks(board: []const []const u8, task: Task) NextTasks {
+    var result = NextTasks.init();
+
+    const previous_direction: Direction = switch (task.entry_direction) {
+        .Vertical => .Horizontal,
+        .Horizontal => .Vertical,
+    };
+    _ = previous_direction;
+
+    switch (task.entry_direction) {
+        .Vertical => {
+            {
+                var current_heat = task.current_heat;
+                inline for (1..11) |delta| {
+                    const new_x = task.x + @as(u8, delta);
+                    if (new_x >= board.len) {
+                        break;
+                    }
+                    current_heat += board[new_x][task.y];
+
+                    if (delta >= 4) {
+                        result.add(.{
+                            .current_heat = current_heat,
+                            .x = new_x,
+                            .y = task.y,
+                            .entry_direction = .Horizontal,
+                        });
+                    }
+                }
+            }
+
+            {
+                var current_heat = task.current_heat;
+                inline for (1..11) |delta| {
+                    if (delta > task.x) {
+                        break;
+                    }
+                    const new_x = task.x - @as(u8, delta);
+                    current_heat += board[new_x][task.y];
+
+                    if (delta >= 4) {
+                        result.add(.{
+                            .current_heat = current_heat,
+                            .x = new_x,
+                            .y = task.y,
+                            .entry_direction = .Horizontal,
+                        });
+                    }
+                }
+            }
+        },
+        .Horizontal => {
+            {
+                var current_heat = task.current_heat;
+                inline for (1..11) |delta| {
+                    const new_y = task.y + @as(u8, delta);
+                    if (new_y >= board[task.x].len) {
+                        break;
+                    }
+                    current_heat += board[task.x][new_y];
+
+                    if (delta >= 4) {
+                        result.add(.{
+                            .current_heat = current_heat,
+                            .x = task.x,
+                            .y = new_y,
+                            .entry_direction = .Vertical,
+                        });
+                    }
+                }
+            }
+
+            {
+                var current_heat = task.current_heat;
+                inline for (1..11) |delta| {
+                    if (delta > task.y) {
+                        break;
+                    }
+                    const new_y = task.y - @as(u8, delta);
+                    current_heat += board[task.x][new_y];
+
+                    if (delta >= 4) {
+                        result.add(.{
+                            .current_heat = current_heat,
+                            .x = task.x,
+                            .y = new_y,
+                            .entry_direction = .Vertical,
+                        });
+                    }
+                }
+            }
+        },
+    }
+
+    //std.debug.print("Next tasks for {any}: {any}\n", .{ task, result.getSlice() });
+
+    return result;
+}
+
+fn solveLines(lines: [][]u8) !usize {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const allocator = arena.allocator();
+
+    for (lines) |line| {
+        for (line) |*char| {
+            char.* = char.* - '0';
+        }
+    }
+
+    const x_max = @as(u8, @intCast(lines.len - 1));
+    const y_max = @as(u8, @intCast(lines[x_max].len - 1));
+    const max_value: u16 = @as(u16, 18) * @max(x_max, y_max) + lines[x_max][y_max];
+
+    var results: Results = [_][150]ResultsByDirection{[_]ResultsByDirection{ResultsByDirection.initFill(max_value)} ** 150} ** 150;
+    var queue_mem = try allocator.alloc(Task, 16 * 1024 * 1024);
+    var tasks = RingQueueWrapper(Task).init(&queue_mem);
+    tasks.add(.{
+        .current_heat = lines[x_max][y_max],
+        .x = x_max,
+        .y = y_max,
+        .entry_direction = .Horizontal,
+    });
+    tasks.add(.{
+        .current_heat = lines[x_max][y_max],
+        .x = x_max,
+        .y = y_max,
+        .entry_direction = .Vertical,
+    });
+
+    var i: usize = 0;
+    while (!tasks.isEmpty()) : (i += 1) {
+        //std.debug.print("Handling task {d}\n", .{i});
+        var current_task = tasks.take();
+        if (results[current_task.x][current_task.y].get(current_task.entry_direction) > current_task.current_heat) {
+            results[current_task.x][current_task.y].set(current_task.entry_direction, current_task.current_heat);
+            for (getNextTasks(lines, current_task).getSlice()) |next_task| {
+                tasks.add(next_task);
+            }
+        }
+    }
+
+    if (false) {
+        std.debug.print("Total tasks done: {d}\n", .{i});
+        for (0..lines.len) |x| {
+            for (0..lines[x].len) |y| {
+                std.debug.print("{d}/{d} ", .{ results[x][y].get(.Horizontal), results[x][y].get(.Vertical) });
+            }
+            std.debug.print("\n", .{});
+        }
+    }
+
+    return @min(results[0][0].get(.Vertical), results[0][0].get(.Horizontal)) - lines[0][0];
+}
+
+pub fn solveAll(reader: anytype) !usize {
+    var result: usize = 0;
+    while (true) {
+        var allocator_buffer: [20000]u8 = undefined;
+        var fba = std.heap.FixedBufferAllocator.init(&allocator_buffer);
+        var allocator = fba.allocator();
+
+        var lines = StackList([]u8, usize, 150).init();
+        var empty_line_reached = false;
+
+        var line_buffer: [1000]u8 = undefined;
+        while (try reader.readUntilDelimiterOrEof(&line_buffer, '\n')) |line| {
+            if (line.len == 0) {
+                empty_line_reached = true;
+                break;
+            }
+            lines.add(try allocator.dupe(u8, line));
+        }
+
+        result += try solveLines(lines.getMutableSlice());
+
+        if (!empty_line_reached) {
+            return result;
+        }
+    }
+}
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+
+    const raw_in = std.io.getStdIn();
+    var buffered_reader = std.io.bufferedReader(raw_in.reader());
+    var reader = buffered_reader.reader();
+    const result = try solveAll(&reader);
+    try stdout.print("{d}\n", .{result});
+}