How to create a mazepart 1 of 2Word文档格式.docx

How to create a mazepart 1 of 2Word文档格式.docx

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∙thenitstartsthemainalgorithm

∙afterthealgorithmfinishedit’sworkitrunsthedraw_maze（）procedurethattranslatestheseriesofnumbersintoapictureofthemaze.

∙finallythemazeisshowedonscreenandtheprogramwaitsfor‘esc’tobepressed.

∙afterthe‘esc’beingpressedtheprogramde-initializes,meaningitclearsallthegraphicstuffanddeletesthemaze（freesthememory）

Thedrawingprocedureworkslikethis:

∙itscansthemazearrayandputsacoloredsquareforeachnumberinthatarray（forexample:

yellowforzero[floor],grayforone[wall]）.Eventuallyyoucanaddmorenumbersandmorecolors（thiswillbeusefulforthemazesolvingalgorithmlater）

∙optionallyyoucanalsoaddanothersmallersquarethatwillbedrawnonthepositiongivenasanargumentofthefunction（thisisusefulfordeterminingthepositionoftheplayerinthemazegame;

I’llexplainitlater）

Nowforthealgorithm:

∙themainalgorithmstartsbycleaningthemazearray（fromallthetrashitmaycontain）.Italsodrawstheouterwalls.

∙nextitsearchestherandomstartandgoalpositions.Theyareleveledtohaveequaloddsontheirrandomness,butcanonlybeplacedoncoordinatesthatconsistofoddnumbers（I’llexplainthislater）.

∙nowtherealalgorithmstarts.Firstitfindsarandomlegalmoveandmakesit（movesthepositioncoordinatetothatplace,setsthecelltofloorandsetsthewallsbehindthatcell）

∙thenitenterstheloopwhichitrepeatsuntilthecountertellshimhefilledthewholemap（thecounterisalwaysright）

∙itfindsthenextlegalrandommoveandifsuchexistsherepeatsthewholeprocedure（movepos.,setfloor,setwalls）

∙ifnolegalmovefounditmakesabackstepandkeepstracingbackuntilitfindsanemptyspacetwocellsawayfromtheoneheiscurrentlypointingto（inotherwords,anemptycelloverthewall）

∙ifhefindssuchacellhemovesthepositioncoordonthewallseparatinghimfromthatcellandturnsittoafloor.Thenormalloopiscontinued.

Explainingthecode:

Toexplainthefirstpartofthetutorial,wearegoingtousethefilecalledmazefull.cpp（thiswasmyfinalresultofseveralattemptstocreatetheprogram）.Firstlet’sexplaintheincludedfiles（usingthe#includedirective）:

∙iostream.h-thisistheC++versionofstdio.h.Inmyprogram,itisusedtoprinterrormessages（forfurtherdetailschecksome‘iostream’andfileI/Otutorials）.NOTE:

ifIweretorunthisprogramasitis（withonlythebasicarguments）theseerrormessageswouldbeprintedoutonscreen.Iuseasimplestreamre-directionbyadding“>

>

log.txt”aftertheprogramname,makingitprintoutitsmessagestoatextfile.Idon’tknowwheredoesthismethodoriginatefrom,butIsawitworkonLinuxsoItriedinDOSanditalsoworked…

∙allegro.h-thisistheheaderofthegraphicslibraryIintendtouseduringthistutorial.Itwillbeusedontwooccasionsinthefirstprogram:

uponinitializationofthegraphicsandinthedrawingprocedurecalleddraw_maze（）…Ifyoure-implementthesetwopartsofthecodetoanotherlibrary,youmaycomment-out（orevendelete）boththisdirectiveandpartsofthecodeyou’vereplaced.

∙stdlib.h-neededforrandomnumbergeneratorandintegertoASCIIandviceversaconversions（srandom（）,random（）,itoa（）,atoi（））.

∙time.h-alsoneededforrandomnumbers.

Alsoonthebeginningofthefileweseethedirectivesthatdefinethemaximumscreenresolution（ifyouareusingWin2korWinNtandcompilethisinAllegro,changethisto320×

200soAllegrocouldchosestandardVGAdrivers,asWin2kandWinNtdon’tsupportVesa）.Wealsoseedefinitionsof“floor”and“wall”whichmakesourprogrameasiertoread（thechararrayisfilledonlywithnumbers,1and0）.Thefirstpartofthefilelookslikethis:

#include

//resolution:

#definemaxx1024

#definemaxy768

#definewall1//intvalueofwallonmap

#definefloor0//intvalueofflooronmap

Thenextpartoftheprogramisadefinitionofaclasscalled“coord”.Forthosethatdon’tknow,aclassisaspecialstructurethatletsusdefineavariablethatholdsseveralothervariablesandfunctionsthatchangethesevariables（socalled“member”variablesandfunctions）.FordetaileddescriptionofclassesIrecommendreadingatutorial,becauseclassesaresomethingeveryintermediateprogrammershouldknowinsideout.Toaccessthesevariables-inside-variableswewillfirsthavetocreatetheso-calledobject（definedasimplevariable,butusingthatclassasthetype;

that’swhythattypeofprogrammingiscalledObjectOrientedprogramming）andaccessitsmembersbywritingthemafteradot,whichisafterthenameoftheobject.Likeso:

coordCoordinateA;

//defininganobject

CoordinateA.x=0;

//accesingthemembervariable"

x"

CoordinateA.ret（0,-1）;

//accesingthememberfunction"

ret（）"

Thecoordinateclassisveryuseful,causenotonlydoesitholdtwodifferentcoordinates（whichpreventsusfordefininguglyvariableslike:

intpos_x,pos_y）,butitalsoprovidesacoupleofveryusefulfunctionsforconversionandautomationofthevaluesofthosevariables.Thismakesourcodemorelogicalandmuchmorereadable.Thefulldefinitionoftheclassisasfollows:

//Coordinateclass.Hasxandycoordinatesandsomehelperfunctions..

classcoord

{

public:

intx,

y;

coord（）:

x（0）,y（0）{}//emptyconstructor（usedtoshowaNULLcoordinate）

coord（inta,intb）:

x（a）,y（b）{}//integerconstructor

coord（constcoord&

c）//copyconstructor

x=c.x;

y=c.y;

}

~coord（）{}//emptydestructor

voidsetW（char*maze,intn）//setsacoordinagivenmazetowall

{maze[x*n+y]=wall;

}

voidsetF（char*maze,intn）//setsacoordinagivenmazetofloor

{maze[x*n+y]=floor;

coordret（intx_of,inty_of）//returnsacoordinateaftervectorchange

{returncoord（x+x_of,y+y_of）;

intm_pos（intn）//returnstecoord.asanindexinthemaze

{returnx*n+y;

operatorint（）//intconverter（usedtodetermineNULLcoordinates）

{returnint（x+y）;

};

//Somesmallhelperfunctions:

intoperator!

=（coorda,coordb）//unequaloperatorforcoordiates

return（a.x==b.x&

&

a.y==b.y）?

0:

1;

intoperator==（coorda,coordb）//equaloperatorforcoordinates

1:

0;

Ihaveaddedthefirsttwohelperfunctionsonpurpose,becausetheyareoperatorsthatoperateontheobjectoftype“coord”（whichisourclass）.Letmeexplaintheclassnow.Aswecanseeitscontentsareprettystraightforward.Allthemembersarepublic,whichmeansthattheycanbeaccessedfromanypartoftheprogramwithnolimitations.

Themembersare:

twointegervariables（xandycoordinates）andacoupleoffunctionsthatdealwitthosevariables.Firstthreefunctionshavenoreturntypeandcarrythenameoftheclassitself.Theyareso-calledconstructors.Eachtimeanobject（variable）oftype“coord”iscreatedacorrespondingconstructorisrun.Theyareusuallyusedtoinitializevalues,butarealsousedfortype-casting（ifwewantforexample,tochangeavalueoftwointegerstoa“coord”wecanjustruncoord（10,20）whichwillcreatea“coord”objectwithoutusingavariable）.Iwillmentiontheuseofconstructorswhenitappearsintheprogram.Also,itisimportanttonoticethattherearethreeconstructors.Wecandothatduetofunctionoverload（inotherwords,youcandefineanyvalueoffunctionswiththesamenameaslongastheyhavedifferentarguments）.

Thefirstconstructorcreatesanemptycoordinate,whichisusefulforusintwocases.First,whenwedeclareanobjectandnotbotherinitializingitwithanyvalues（likecoorda,b,temp;

andsoon）.Thesecondtimeweusethisconstructoriswhenwewanttoinformourprogramthatacertaincoordinateisnotvalid.Becausethecellatcoordinate0,0isalwayssettowallatthebeginningoftheprogram（beforethestartofthealgorithm）andisneveraccessedafterthat,weareallowedtousethatvalueasatypeofNULLcoordinate.AnotherthingwecandoisaddingthetwovaluesofacoordinateandiftheyequalzerothenwearesurethatwearedealingwithourNULLcoordinate（noothercoordinate,whensummedgiveszero）.Asyoumayhavenoticed,thelastmemberfunctionofourclassisanintegertypeconverter（aspecialfunctionthatconvertsacoordinatetoanint.Toactivateitallwehavetodoiswriteint（coord（20,30））or（int）coord（20,30））.Thesetwofunctionsputtogethergiveusaneasywaytodealwithinvalidvalues.Forexample,ifwegiveourprogramtofindthenextrandommoveandthereisnosuchmove,allthatsuchafunctionhastodoisreturnacoord（）（emptycoordinate）andallwehavetodoischeckwhetherthe（int）r（ifristhereturnedcoordvalueofthefunction）isnon-equaltozero.Ifit’strue,thenwecanusethatcoordinate.Ifnotwehavetofindanotherwayaround.Thisisjustasimpletrick.Ofcoursethereareotherwaystodothat,butthisseemsgoodenoughtome（bothincodereadabilityandprogramefficiency）.

Thesecondconstructortakestwointegersasarguments.Itisusedwhenwewanttocreateanobjectandinitializeitwithsomesensiblevalues（likecoorda（10,10）,b（100,9）;

andsoon）.Itcanalsobeusedtosendvaluesdirectlyasobjec