【Edabit 算法 ★★★★★】【两个大整数相加】Recursion: Sum of Two Numbers (With A Twist!)

Recursion: Sum of Two Numbers (With A Twist!)

Instructions

This is an "expert" challenge!!! Why is a sum of two numbers an "expert" challenge!!! Well, the numbers can have 1000 digits or even beyond such count...

So, what's the twist? You have to do the summation as if you're doing it manually on a piece of paper, thus, the conversion of the numeric string to numeric literal is basically disallowed.

Examples

sum("12132000", "12171979") // "24303979"

sum("4666", "544") // "5210"

sum("1521512512512512515", "898989898989988998899898") // "898991420502501511412413"

sum("5125515215521515", "125261616261626") // "5250776831783141"

sum("6666666666666666666666666666", "99999999999999999999999") // "6666766666666666666666666665"

sum("123456789123456789123456789", "987654321987654321987654329876543") // "987654445444443445444443453333332"

Notes

• Remember how to sum two numbers ON A PAPER, such is the process.
• Your function must run in less than 10 seconds because it has a time limit.
• The use of Number class such as BigInt is disallowed -- it will defeat the purpose and the level of difficulty associated to this challenge.
• You are expected to solve this challenge recursively.

Solutions

const sum = (a, b,c=0) => {
    if(!a && !b && c == 0){
        return ''
    }
    let aa = (a)?(a.slice(-1)-0):0;
    let bb = (b)?(b.slice(-1)-0):0;
    let s = aa + bb + c
    c = s>9?1:0;
    return sum(a.slice(0,-1),b.slice(0,-1),c)+(s%10)
}

TestCases

let Test = (function(){
    return {
        assertEquals:function(actual,expected){
            if(actual !== expected){
                let errorMsg = `actual is ${actual},${expected} is expected`;
                throw new Error(errorMsg);
            }
        },
        assertNotEquals:function(actual,expected){
            if(actual === expected){
                let errorMsg = `actual is ${actual},${expected} is expected,they are equals`;
                throw new Error(errorMsg);
            }
        }

    }
})();

const isRecursive = src => (`${src}`.match(RegExp(`${src.name}`, 'gm'))||[]).length > +(/function/.test(src))
Test.assertNotEquals(isRecursive(sum), false, "Recursion is required!")

let [actualParam, expectedParam] = [
    [
        ["12132000", "12171979"], ["4666", "544"], ["1521512512512512515", "898989898989988998899898"],
        ["5125515215521515", "125261616261626"], ["6666666666666666666666666666", "99999999999999999999999"],
        ["123456789123456789123456789", "987654321987654321987654329876543"], ["51", "512"],
        ["46580672134861691487886856201063433530317493541984174240640117078384844027455455145995264175402994424834479825796316174329467969102257360195385044875023188313698661902232816682563450684527972706431205", "20129647448213526330992199933412026717951269059875880213489467074335368047371342207724579931208231032969760043956811494704380198848377355718984761723730087673439394159054420344427904875384087249296946"],
        ["9128242816391792390367394318238609154929962550133827657886034828979294413033450307173793450924762143201991300288127408763421237279633517929936847079257713141254694944681428142978110027357322312404627593110196423560326537881370897768020382035189644680256824659171348515208671339529370866296929702167647163038519576331084019822103309755374561623148508523431380245253765653509318684179663600476971689801", "5920641803160990513445202815794518152101247319199211634010324208708552138569594568355624738331704740605556159925350097568289164018471525773848461636579024644391854277092707811953956319566890527925989019562020260846251250663758330856266051985217733863782039893158278545291027890391152027767054280498870038607952519452004179810592466387736659835203110761590431605238080432136468832137768846891022675668"],
        ["24050292702239538714424762926989391091054882494797379961190995916419743076846190252322346159955367441832937735205583340798028856059731163836333572978411075895848661770468080051146869104337532213474993926921843996913706778627924709600100860461421587774140722793995230660233453392717776973617724296276959982403528208646617679528431859423982314682036555772485961534695291544266936268924447065901465864784710200365748971482974309578528938725051499783831735126491173069337708438252812165533370751831832345511906521502270947947504198101881866181323122256768406228518806385974069302887460096561970477705646199939356606923830372891944037065847071308700107176794261922547322922787636783283829766004529060524539701495229943211611134317723328686844713489223961776582365551050940511119736023799724295560712462775", "32509558457800134082157248923945369106923458582597107662799282973299414325101867489152494482453431986091527569819907127801971978514325573048496062254539304686542784848485721075326183780905103371293505027494462848297668132430517455611475977074377557603798687767852907762254040565866554962529868705211874976201522692137999060766380670853123585546115851899681725949430620582898894763596679656710337017496618525630124192131724949516793735384953877012134805554272494110981312910720545085389502607669244051838541600298937410166860469735980721786025686375273866096353307350361733480286161315578348192126560652007559649899391482681958298876030894402469363045420883354390088168624736238621292726748213941087878476447239860986699971354976451472810499473465596980950104110861804910439253305564075282187561761831"], ["6809632763916891310120420620586174664812635530867937840217826224568347127990297761160448320170180761000408251375466103628257285208000720825374647976159883503477330018358281993325677527017557058976068333642868984291739483975621870841667306204393840341405348294943813620516550885907643492592684427984599974017532776047374095558566398217709965020793366640224373810304569301398035374905004719899959454164388545839944663454514841628001498947789419801699846006819006975473515954356883318037820103882153723720601881130291354697184471999967716687686218472392686266650318568026273517115609143992129773683289728842208471476663161973115343223846428988702456038387814984825150310010062042877806640480710525528241328472095324930106698917227353621406980530110747055257101350540514070478171412772633866196018240727864894180766177622426511795549818029880640303307250349733954619463752541929370662897223878043296358089043269919860180819045946942402216596728187295625046088616265162395417587774677163023091414012232562","8580486073000341176464481569509088314164648516198308588306341581886828084652373143824178061446100845207932260299989735098857835077503613944792671258723699144053082578718738452102088425930223680001667115358790806513480705990372645625620985201064789499679080382290229510353519900434457951354146351017356497038201676685010533295544810336326460878234636045306593283716955770214654833569407250862467764241301491075773878798755773232056371316349556337923582112418745691372603517681014116333538448075872043025194944464917374343870889032601696418177538646357828263727642286052251539150438138687143116934852022178306775340622808992992303183802309493297583818627523253611781850609208464293666564468773980578995182119812585094120227322948794646916387478317146222403428768533848504528795446827274517795896686680232498391880209937677390643332411043134407239601699748922010617022901854909440001914242164998598960486713118948710525156592829968225269277615537170861633579862039532587858207573589726753466950083211842"]
    ], [
        "24303979",
        "5210",
        "898991420502501511412413",
        "5250776831783141",
        "6666766666666666666666666665",
        "987654445444443445444443453333332",
        "563",
        "66710319583075217818879056134475460248268762601860054454129584152720212074826797353719844106611225457804239869753127669033848167950634715914369806598753275987138056061287237026991355559912059955728151",
        "15048884619552782903812597134033127307031209869333039291896359037687846551603044875529418189256466883807547460213477506331710401298105043703785308715836737785646549221774135954932066346924212840330616612672216684406577788545129228624286434020407378544038864552329627060499699229920522894063983982666517201646472095783088199632695776143111221458351619285021811850491846085645787516317432447367994365469",
        "56559851160039672796582011850934760197978341077394487623990278889719157401948057741474840642408799427924465305025490468600000834574056736884829635232950380582391446618953801126473052885242635584768498954416306845211374911058442165211576837535799145377939410561848138422487493958584331936147593001488834958605050900784616740294812530277105900228152407672167687484125912127165831032521126722611802882281328725995873163614699259095322674110005376795966540680763667180319021348973357250922873359501076397350448121801208358114364667837862587967348808632042272324872113736335802783173621412140318669832206851946916256823221855573902335941877965711169470222215145276937411091412373021905122492752743001612418177942469804198311105672699780159655212962689558757532469661912745421558989329363799577748274224606",
        "15390118836917232486584902190095262978977284047066246428524167806455175212642670904984626381616281606208340511675455838727115120285504334770167319234883582647530412597077020445427765952947780738977735449001659790805220189965994516467288291405458629841084428677234043130870070786342101443946830779001956471055734452732384628854111208554036425899028002685530967094021525071612690208474411970762427218405690036915718542253270614860057870264138976139623428119237752666846119472037897434371358551958025766745796825595208729041055361032569413105863757118750514530377960854078525056266047282679272890618141751020515246817285970966107646407648738482000039857015338238436932160619270507171473204949484506107236510591907910024226926240176148268323368008427893277660530119074362575006966859599908383991914927408097392572646387560103902438882229073015047542908950098655965236486654396838810664811466043041895318575756388868570705975638776910627485874343724466486679668478304694983275795348266889776558364095444404"
    ]
]
for (let i in actualParam) Test.assertEquals(sum(...actualParam[i]), expectedParam[i])