计算机科学与导论第13章.pdf

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1、CHAPTER13FileStructures(SolutionstoReviewQuestionsandProblems)ReviewQuestionsQ13-1.Thetwoaccessmethodsaresequentialandrandom.Q13-2.Theoldmasterfileisthefilethatshouldbeupdated;thenewmasterfilecon-tainsthecurrentdata(thedatafromtheoldmasterfileincludinganychange

2、sthatweremadeduringtheupdateprocess).Q13-3.Thetransactionfilecontainschangesthatshouldbemadetotheoldmasterfile.Q13-4.Toaccessarecordinafilerandomly,weneedtoknowtheaddressoftherecord.Q13-5.Theindexisatablethatrelatesthekeysofthedataitemstotheaddressesinthefilewh

3、erethedataarestored.Q13-6.Indirecthashing,thekeyistheaddressoftherecordinthefile.Q13-7.Inmodulodivisionhashing,thekeyisdividedbythefilesize.Theremainderplus1isusedastheaddressoftherecordinthefile.Q13-8.Indigitextractionhashing,certaindigitsareremovedfromthekeya

4、ndusedastheaddressoftherecord.Q13-9.Acollisionoccurswhentwohashedrecordhavethesameaddress.Thethreecollisionmethodsareopenaddressing,linkedlistresolution,andbuckethash-ing.Inopenaddressing,theprimeareaissearchedforanunoccupiedaddress.Inlinkedlistresolution,thefi

5、rstrecordisstoredinthehomeaddress,butitcontainsapointertothesecondrecord.Inbuckethashing,agroupofrecordsarestoredinabucketswhicharelocationsthatcanaccommodatemorethanonerecord.Q13-10.Atextfileisafileofcharacterswhileabinaryfileisacollectionofdatastoredintheinte

6、rnalformatofthecomputer.12ProblemsP13-1.Thefilesareshownbelow:NewMasterFileErrorFileKeyNamePayRateActionKeyNamePayRate14JohnWu17.00A17MarthaKent17.0016GeorgeBrown18.0017DucLee11.0026TedWhite23.0031JoanneKing28.0089MarkBlack19.0090OrvaGilbert20.0092BetsyYellow14

7、.00P13-2.Bothdatafileandindexfileareshownbelow.IndexDatafileKeyAddressAddressKeyNameDept.077654004000123453JohnAdamCIS093245003001114237TedWhiteMTH114237001002156734JimmyLionsENG123453000003093245SophieGrandsBUS156734002004077654EvePrimaryCIS256743005005256743E

8、vaLindensENG423458006006423458BobBauerECOP13-3.a.(14232mod41)+1=5+1=6b.(12560mod41)+1=14+1=15c.(13450mod41)+1=2+1=3d.(15341mod41)+1=7+1=8P13-4.a.1422=20164→16b.1252=15625→62