C++程序设计 - 第05讲

C++程序 设计 领导形象设计圆作业设计ao工艺污水处理厂设计附属工程施工组织设计清扫机器人结构设计 西北工业大学软件与微电子学院杨帆Part2:ControlStatements,MethodsandArrays Chapter4:ControlStatements Chapter5:FunctionsandanIntrotoRecursion Chapter6:ArraysandVectors Chapter7:PointersChapter5:FunctionsandanIntrotoRecursion divideandconquer（分而治之）developandmaintainalargeprogramistoconstructitfromsmall,simplepieces,orcomponents.ProgramComponentsinC++ C++programsaretypicallywrittenbycombiningnewfunctionsandclassesyouwritewith“prepackaged”functionsandclassesavailableintheC++StandardLibrary. Functionsyouwritearereferredtoasuser-definedfunctionsorprogrammer-definedfunctions. Themotivationsformodularizingaprogramwithfunctions： divide-and-conquerapproach softwarereuse toavoidrepeatingcode makestheprogrameasiertodebugandmaintain afunctionisinvokedbyafunctioncall,andwhenthecalledfunctioncompletesitstask,iteitherreturnsaresultorsimplyreturnscontroltothecaller.GlobalFunctions Sometimesfunctions,suchasmain,arenotmembersofaclass.Suchfunctionsarecalledglobalfunctions. Likeaclass’smemberfunctions,thefunctionprototypesforglobalfunctionsareplacedinheaders,sothattheglobalfunctionscanbereusedinanyprogramthatincludestheheaderandthatcanlinktothefunction’sobjectcode.MathLibraryFunctions The<cmath>headerprovidesacollectionoffunctionsthatenableyoutoperformcommonmathematicalcalculations. sqrt(900.0); Functionargumentsmaybeconstants,variablesormorecomplexexpressions. cout<<sqrt(c+d*f)<<endl;FunctionPrototypes Afunctionprototype“函数原型”(alsocalledafunctiondeclaration“函数声明”)tellsthecompilerthenameofafunction,thetypeofdataitreturns,thenumberofparametersitexpectstoreceive,thetypesofthoseparametersandtheorderinwhichtheparametersofthosetypesareexpected.intmaximum(int,int,int);FunctionSignatures Theportionofafunctionprototypethatincludesthenameofthefunctionandthetypesofitsargumentsiscalledthefunctionsignature. Thefunctionsignaturedoesnotspecifythefunction’sreturntype. Functionsinthesamescopemusthaveuniquesignatures.FunctionReturnValueintmaximum(int,int,int);intx=maximum(3,5,9);voidmaximum(int,int,int);cout<<maximum(5,4,0);intmaximum(intx,inty,intz){intmaximumValue=x;if(y>maximumValue)maximumValue=y;if(z>maximumValue)maximumValue=z;returnmaximumValue;}intmain(){inta,b,c,d;a=b=c=d=0;d=maximum(a,b,c);}05-01.cppintmaximum(intx,inty,intz)d=maximum(a,b,c); formalparametervs.actualparameter Therearethreewaystoreturncontroltothepointatwhichafunctionwasinvoked. Ifthefunctiondoesnotreturnaresult(i.e.,ithasavoidreturntype),controlreturnswhentheprogramreachesthefunction-endingrightbrace,orbyexecutionofthestatement“return;” Ifthefunctiondoesreturnaresult,thestatement“returnexpression;”evaluatesexpressionandreturnsthevalueofexpressiontothecaller.ArgumentCoercion Animportantfeatureoffunctionprototypesisargumentcoercion(“参数转换”)—i.e.,forcingargumentstotheappropriatetypesspecifiedbytheparameterdeclarations. voidTest(doublea); Test(3);ArgumentPromotionRules Sometimes,argumentvaluesthatdonotcorrespondpreciselytotheparametertypesinthefunctionprototypecanbeconvertedbythecompilertothepropertypebeforethefunctioniscalled. TheseconversionsoccurasspecifiedbyC++’spromotionrules. thefundamentaldatatypesinorderfrom“highesttype”to“lowesttype.” Convertingvaluestolowerfundamentaltypescanresultinincorrectvalues. Functionargumentvaluesareconvertedtotheparametertypesinafunctionprototypeasiftheywerebeingassigneddirectlytovariablesofthosetypes. square(4.5)returns16,not20.25 RandomNumberGeneration usingtheC++StandardLibraryfunctionrand05-02.cpp05-03.cpp05-04.cpphttp://www.cnblogs.com/afarmer/archive/2011/05/01/2033715.htmlC/C++中产生随机数(rand,srand用法)实验06：函数初步与随机数阅读Self-ReviewExercisesandAnswers（6.1～6.10）必做题WriteafunctionintegerPower(base,exponent)thatreturnsthevalueofbaseexponent.Forexample,integerPower(3,4)=3*3*3*3.Assumethatexponentisapositive,nonzerointegerandthatbaseisaninteger.Donotuseanymathlibraryfunctions.Writeaprogramthatplaysthegameof“guessthenumber”asfollows:Yourprogramchoosesthenumbertobeguessedbyselectinganintegeratrandomintherange1to1000.Theprogramthendisplaysthefollowing:Ihaveanumberbetween1and1000.Canyouguessmynumber?Pleasetypeyourfirstguess.Theplayerthentypesafirstguess.Theprogramrespondswithoneofthefollowing:1.Excellent!Youguessedthenumber!Wouldyouliketoplayagain(yorn)?2.Toolow.Tryagain.3.Toohigh.Tryagain.Iftheplayer’sguessisincorrect,yourprogramshouldloopuntiltheplayerfinallygetsthenumberright.YourprogramshouldkeeptellingtheplayerToohighorToolowtohelptheplayer“zeroin”onthecorrectanswer. 实验作业要求： 当次实验课结束前务必提交实验作业 实验作业要求压缩打包，压缩文件命名方式为：“学号姓名.rar”，例如“2013303281刘怡芸.rar” 将实验作业提交给实验课老师Introducingenum Anenumeration,introducedbythekeywordenumandfollowedbyatypename(inthiscase,Status),isasetofintegerconstantsrepresentedbyidentifiers. Thevaluesoftheseenumerationconstantsstartat0,unlessspecifiedotherwise,andincrementby1. AnotherpopularenumerationisenumMonths{JAN=1,FEB,MAR,APR,MAY,JUN,JUL=0,AUG,SEP,OCT,NOV,DEC}; whichcreatesuser-definedtypeMonthswithenumerationconstantsrepresentingthemonthsoftheyear.Thefirstvalueintheprecedingenumerationisexplicitlysetto1,sotheremainingvaluesincrementfrom1,resultinginthevalues1through12. Anyenumerationconstantcanbeassignedanintegervalueintheenumerationdefinition,andsubsequentenumerationconstantseachhaveavalue1higherthantheprecedingconstantinthelistuntilthenextexplicitsetting.05-05.cppFunctionswithEmptyParameterLists InC++,anemptyparameterlistisspecifiedbywritingeithervoidornothingatallinparentheses. Theprototypespecifiesthatfunctionprintdoesnottakeargumentsanddoesnotreturnavalue. voidprint(); intprint(void);DefaultArguments It’scommonforaprogramtoinvokeafunctionrepeatedlywiththesameargumentvalueforaparticularparameter.Insuchcases,youcanspecifythatsuchaparameterhasadefaultargument,i.e.,adefaultvaluetobepassedtothatparameter. mustbetherightmost(trailing)arguments mustbespecifiedwiththefirstoccurrenceofthefunctionname—typically,inthefunctionprototype canbeanyexpression,includingconstants,variablesorfunctioncalls05-06.cppFunctionCallStack StackandQueue(栈与队列) Stacksareknownaslast-in,first-out(LIFO)datastructures—thelastitempushed(inserted)onthestackisthefirstitempopped(removed)fromthestack. Queues—first-in,first-out(FIFO)05-07.cppInlineFunctions Placingthequalifierinlinebeforeafunction’sreturntypeinthefunctiondefinition“advises”thecompilertogenerateacopyofthefunction’sbodycodeinplace(whenappropriate)toavoidafunctioncall. Thecompilercanignoretheinlinequalifierandtypicallydoessoforallbutthesmallestfunctions.inlinedoublecube(constdoubleside){returnside*side*side;}intmain(){doublesideValue;cout<<"Enterthesidelengthofyourcube:";cin>>sideValue;cout<<"Volumeofcubewithside"<<sideValue<<"is"<<cube(sideValue)<<endl;}FunctionOverloading C++enablesseveralfunctionsofthesamenametobedefined,aslongastheyhavedifferentsignatures. Thisiscalledfunctionoverloading. Functionoverloadingisusedtocreateseveralfunctionsofthesamenamethatperformsimilartasks,butondifferentdatatypes.__Z6squrei__Z6squred_main05-08.cpp Overloadedfunctionscanhavedifferentreturntypes,butiftheydo,theymustalsohavedifferentparameterlists. Again,youcannothavetwofunctionswiththesamesignatureanddifferentreturntypes. voidf(); intf(); inti=f(); f(); functionmainiscannotbeoverloaded.voidS();voidS(int);voidS(double,double=1.2);voidMax(double);intmain(){　S(2.4);　return0;}Recursion(递归) Arecursivefunctionisafunctionthatcallsitself,eitherdirectly,orindirectly(throughanotherfunction). n!＝n×(n－1)×(n－2)×…×1 factorial=1; for(intcounter=number;counter>=1;--counter) factorial*=counter; n!=n×(n－1)!05-09.cpp FibonacciSeries 0,1,1,2,3,5,8,13,21,… fibonacci(0)=0 fibonacci(1)=1 fibonacci(n)=fibonacci(n–1)+fibonacci(n–2)05-10.cpp Recursionvs.Iteration Recursionhasnegatives.Itrepeatedlyinvokesthemechanism,andconsequentlytheoverhead,offunctioncalls.Thiscanbeexpensiveinbothprocessortimeandmemoryspace. Eachrecursivecallcausesanothercopyofthefunction(actuallyonlythefunction’svariables)tobecreated;thiscanconsumeconsiderablememory. Iterationnormallyoccurswithinafunction,sotheoverheadofrepeatedfunctioncallsandextramemoryassignmentisomitted.实验07：递归函数必做题Writearecursivefunctionpower(base,exponent)that,wheninvoked,returnsbaseexponent. Forexample,power(3,4)=3*3*3*3.Assumethat exponentisanintegergreaterthanorequalto1. Hint:Therecursionstepwouldusetherelationship baseexponent=base×baseexponent–1andtheterminating conditionoccurswhenexponentisequalto1,because base1=base.Thegreatestcommondivisorofintegersxandyisthelargestintegerthatevenlydividesbothxandy.Writearecursivefunctiongcdthatreturnsthegreatestcommondivisorofxandy,definedrecursivelyasfollows:Ifyisequalto0,thengcd(x,y)isx;otherwise,gcd(x,y)isgcd(y,x%y),where%isthemodulusoperator. [Note:Forthisalgorithm,xmustbelargerthany.]选做题了解研究“汉诺塔问题”，假设移动一片黄金圆盘需要1秒钟，设计算法并编写程序计算移动64片黄金圆盘所需的时间。http://blog.csdn.net/geekwangminli/article/details/7981570 实验作业要求： 当次实验课结束前务必提交实验作业 实验作业要求压缩打包，压缩文件命名方式为：“学号姓名.rar”，例如“2013303281刘怡芸.rar” 将实验作业提交给实验课老师