频道容器被设计用于保存同一类型多个对象vectorstring

PartI(#5.1-vectorandhowtoclassifyelementsinahowtouse torforsequential tor实现顺序introduceanewcontainerclass/temteclassSeparatingStudentsintoWewantowriteafunctiontoseparatestudentsintocategories:pass(≥60)andfail(<CanyouseetheleakinCanyouseetheleakinthesetwoProblemofTheCategorizingDuetotheuseofpassandfailvectors,needsamemoryspaceatleasttwicethesizeofToaddressthememory cancelthepass Eventually,studentsonlystoresthepassedstudentsandstoresthefailThevectorclassoffersamemberfunctionerasetodeleteanelementfromavector.TheeraseTheerasefunctioninthevector parameter: torrefertotheelementtobe side-effect:causingreassignmentofthefollowing CanyoufindouthowtheloopchangestheindexwhenpassedandfailedTheRevisedCanweuseavariable(e.g.,size)tostorethesizeofbeforetheloopandsetthewhileconditionas(i!=size)Efficiencyofvectoris becausewecanvisitanyelementinavectorbyitsindex: it’seasytoreadand it’sslowtoinsertordeleteelements,exceptforthevectorHence,theerasefunctioninthevectorclassisnotsoefficient,especiallywhenthevectorislarge.Useamorepropercontainer(i.e.,onewithsequentialUsea NotionofIBeforechangingstudentsintosequentialcontainer,sesequentialcontainerdoesn’tsupportvisitbyindex,wemustrevisetheprogramsothatitusesitorsforsequentialvisit.在将students更改为顺序容器前，由于顺序容器不支持索引，需要修改程序，使它运用itor进行顺序。An torisavalue identifiesacontainerandanelementina let hevaluestoredinthe perationsformovingbetween restrictstheavailableoperationstotheefficientTypeofITherearetwotypesof const tor: nlyreadaccesstothe tor:providebothreadandwriteaccessestothetortor An torcanbeautomaticallyconvertedtoaconst Anconst torcannotbeconvertedtoan vector<double>vector<double>torciter=OperationsofIiter=Assigntherightoperandoprtoiter1!=iter2iter1==Comparetheequalityofiter1andComparetheinequalityofiter1andrementiterbyAccesstheelementreferredbyAnExampleofIforfor(vector<Student_info>::const_iteriter=iter!=d();cout<<(*iter).name<<for(vector<Student_info>::size_typei=0;i!=students.size();++i)cout<<students[i].name<<Canweuse*toreIsthereanyshort-handwaytowriteTheRevisedTheaboveprogramhassixexpressionsthatinvolveiter.Canyouexintheirmeanings?ANewTypelistisacontaineraswellasatemte listisdefinedintheheader listisavirtualclassuntilitsdatatypeisnamedby<>std::list<double>std::list<double> torbutnot listisasequentialcontainercharacterizedbyfastinsertion/deletionanywherewithinthecontainer; listsharesanumberofsimilaroperationswithbegin,end,push_back,erase,Theireffectsareidentical,buttheimplementationsareveryThelistVersionofAnyAnyweenofextract_fails?SomeImportantDifferenceBetweenSomeImportantDifferenceBetweenvectorandlist(PAGE1)Deletinganelementinsideavectorcausessubsequentelementstomove,andhenceinvalidatesalltheitorsofsubsequenements.Insertinganelementinsidethevectorcancausereallocationofthevector,andhenceinvalidatestheitorsofallelements.在vector中元素可引起为vector重新分配空间导致有元的itor。Neitherinsertionordeletionfalsifiestheitorsoftheotherelements.或删除list中的元素不会使其它元素的Wecanusethesortfunctiondefinedin<algorithm>tosortavectorinnon-decreasingorder.Alistusesthememberfunctionsortoflistforsortinginnon-decreasinge.g.,sortavectorvecandalistLintheorderdefinedbythecomparesort(vec.begin(),sort(vec.begin(),vec.end(),*Thetwocomparefunctionsaredefinedinthesamewayandarebothoptional(可选WhyInordertochangethestructureforholdingstudents’datafromvectortolist,wemustrevisethegradingprogramthoroughly,whichisnotaneasytask.TherevisioncanimprovetheefficiencyofFrom ample,weshouldknow PartII(#5.6-ManipulatingSofar,wehavelearntafewoperationson createa//strisanullstr=//strisinitialized//strisinitializedasncopiesofcharacterstr1+str1+ writeacoutcout<< sizeastringAsAstringcanbeviewedasaspecialkindof itcontainsonly itsupportssome,butnotall,ofthecontainer itsupportsindexingand str[i]//iisintherangeofvisitthestr[i]//iisintherangeof tethrowastring//anythingweneedtodotoevery}MotivationforSplittingItisacommoncomputationtobreakastringintowords,separatedbywhitespaces(i.e.,space,tab,backspace,ortheendoftheline). oIam o”,“I”,“am”,“from”, ThebasicideaofthesplittingStartingfromthe1stcharacterofthestring,dotherecordtheindexofthe1stnon-whitespacecharacterwemetasrecordtheindexofthenextwhitespace srecordthecharactersin[i,j)asawordandaddittoastringmoveontothenextContinueuntilwe oftheTheThesplitFunction WhyWhytosetthetypesofreturnedvalueandparametersthisTheThesplitFunctionAB TheisspaceABisdefinedinindicatesiftheargumentisawhitespace. ThewhilestatementinANOTa ThewhilestatementinBaC ForpartCequals.size().wheni!=j,Ctakesasubstringofsfromitojandappendittowords,whichisavectortostorewordsfroms. ThesubstrtakeasubstringstartingfromiandhasalengthofTestThesplitThestringlibraryoffersafunction getlinereadsinputuntilit ofthe getlakestwo anistream¶meter,fromwhichinputis astring¶meter,inwhichinputis It’salsocalledthedriverfunctionofthesplitfunction.CharacterAcharacterpicture(字符图象isarectangleofcharactersthatcanbedisyed.(e.g.,theframedgreetingmessageisacharacterInthefollowingslides,wewilllearnmoreaboutstringbywritingfunctionsto: framestringsinagivenvectortoformacharacter concatenatetwocharacterpictures concatenatetwocharacterpicturesTheTheframeFunctionThisisanWedesigntheframefunction

Thisisan illustrate takeoneparameterv,whichstoresthegiven returnastringvectorret,inwhicheachstringisalineinthecharacterpicture.返回一个stringvectorret，其中每个stringsizeeachstringinvandrecordthelargestsizeisbuildtheborderlineasastringbordercontainsasterisksandappendittoretasthetopborderofthebuildtheinteriorlinesinthepusheachinteriorlineintopushtheborderintoretagainasthebottomborderoftheWefirstwriteafunctionwidthtoobtainthe umsizeofstringsinthevectorv.•••WhywesetthetypeofthesconstWhywedefinemaxlentohavetypeWhyWhywesetthetypeofthesconstWhatdoesstring(maxlen-v[i].size(),'')TheThevcatFunction

Thevcatfunctioniswrittentoconcatenatetwocharacterpicturesvertically(垂直地). take2parameterstopandbottom,bothofwhicharestringvectors; returnastringvector,inwhicheachstringisalineintheconcatenatedpicture. Thealgorithmbehindvcatiseasy.Justappendallthestringsintopandbottomintoret.WhyWhywesetthetypesofthetwoparametersasconstTheThehcatFunctionThisisThisisan*Thisisan* * *illustrate*

Thehcatfunctioniswrittenforconcatenatetwocharacterpictureshorizontally(水平地).Thehcatfunctionisdesignedrecordthewidthoftheleftpicturewidth1=buildtheithlineoftheconcatenatedpictureas buildanullstring ifleft[i]exists,copyleft[i]into appendswidth1–s.size()spacesto ifright[i]exists,copyright[i]into pushsintothestringvectorreturnedby testep2)untiliexceedsthelargernumberbetweenthesizesofleftandright; TheproTheprograminthetextbookisabitdifferentfromhere.Pleasereadandunderstandit.MissionBookOurlessononlycoversthemostimport hapter5.Pleasereadthetextbookcarefullyformoredetails,especially5.9. Toencouragestudentschallenginglargerproblems,theexercisesafterChapter5isclassifiedinto2groupsbasedontheirdifficulty. BasicGroup:Ex5-6,5-7,5- ImprovedGroup:Ex5-1,5-3,5-5,5-9,5-10,5- 1exerciseintheimprovedgroup=2exercisesinthebasicExperimentReport:Ex5-2(submiton4th,AboutEx5-Youwillwritetwo oneusesvectortostorestudents’ oneuseslisttostorestudents’Theadvantageofthelistversionisonlyobviouswhenthenumberofstud