CS11001/CS11002ProgrammingandDataStructures

(PDS)(Theory:3-0-0)

Teacher:SourangshuBha@acharyasourangshu@gmail.com

h@p://cse.iitkgp.ac.in/~sourangshu/

DepartmentofComputerScienceandEngineeringIndianInsJtuteofTechnologyKharagpur

AcompleteCprogram

voidPRINT(){

prin1(“HelloEverybody!!!\n”);}

voidPRINT_I(intb){

prin1(“%d\n”,b);}

voidPRINT_F(floatp,floatq){

prin1(“%2.1f%2.2f\n”,p,q);}

/*prog.c*/#include<stdio.h>voidPRINT();voidPRINT_I(int);voidPRINT_F(float,float);voidmain(){

inta=10;floatx,y;scanf(“%d%d”,&x,&y);PRINT();PRINT_I(a);PRINT_F(x,y);

}

CompilaJonandExecuJon

$cc–Wallprog.c$$./a.out2.343.45HelloEverybody!!!102.33.45$

AcompleteCprogram/*prog.c*/#include<stdio.h>voidPRINT();voidPRINT_I(int);voidPRINT_F(float,float);voidmain(????){

inta=10;floatx,y;scanf(“%d%d”,&x,&y);PRINT();PRINT_I(a);PRINT_F(x,y);

}

voidPRINT(){

prin1(“HelloEverybody!!!\n”);}

voidPRINT_I(intb){

prin1(“%d\n”,b);}

voidPRINT_F(floatp,floatq){

prin1(“%2.1f%2.2f\n”,p,q);}

CommandLineArguments

•  Commandlineargumentsmaybepassedbyspecifyingthemundermain().

intmain(intargc,char*argv[]);

Argument Count Array of Strings

as command line arguments including the command itself.

Passingparameterstomain()

#include<stdio.h>intmain(intargc,char*argv[]){inti;for(i=0;i<argc;i++){prin1("%d:%s\n",i,argv[i]);}return0;}

$cc-Wallwk13_commandline.c$./a.out0:./a.out$./a.outHI0:./a.out1:HI$./a.outIndianInshtuteofTechnology0:./a.out1:Indian2:Inshtute3:of4:Technology

Passingparameterstomain()

#include<stdio.h>intmain(intargc,char*argv[]){inti;for(i=0;i<argc;i++){prin1("%d:%s\n",i,argv[i]);}return0;}

$Jme./a.outIndianInsJtuteofTechnology0:./a.out1:Indian2:Inshtute3:of4:Technologyreal0m0.002suser0m0.001ssys0m0.001s

Passingparameterstomain()#include<stdio.h>intmain(intargc,char*argv[]){inti;for(i=0;i<argc;i++){prin1("%d:%s\n",i,argv[i]);}return0;}

$./a.outAnirban218.30:./a.out1:Anirban2:213:8.3

./a.out Anirban 21 8.3

argc=4

./a.out Anirban

21 argv

8.3

LibraryfuncJonsscanf()

•  Headerfile:–  #include<stdio.h>

•  Funchonprototype:–  intsscanf(constchar*str,constchar*format,...);

•  Conversioncharacterissameasscanf().

Passingparameterstomain()

#include<stdio.h>intmain(intargc,char*argv[]){inti;for(i=0;i<argc;i++){prin1("%d:%s\n",i,argv[i]);}return0;}

#include<stdio.h>intmain(intargc,char*argv[]){charname[20];intage;floatcgpa;sscanf(argv[1],"%s",name);sscanf(argv[2],"%d",&age);sscanf(argv[3],"%f",&cgpa);prin1("%s%d%f\n",

name,age,cgpa);return0;}

$./a.outAnirban218.30:./a.out1:Anirban2:213:8.3$

$./a.outAnirban218.3Anirban218.300000$

FuncJonstoconvertstringstonumbers

•  Oncewe'vegotastringwithanumberinit(eitherfromafileorfromtheusertyping)wecanuseatoioratoftoconvertittoanumber

•  Thefunchonsarepartofheaderfilestdlib.hchar numberstring[]= "3.14"; int i; double pi; pi= atof (numberstring); i= atoi ("12"); Bothofthesefunchonsreturn0iftheyhaveaproblem

Example:AveragefromCommandLine

#include<stdio.h>#include<stdlib.h>intmain(intargc,char*argv[]){floatsum=0;inti,num;num=argc-1;for(i=1;i<=num;i++) sum+=atof(argv[i]);prin1("Average=%f\n",sum/(float)num);return0;}

$ ./a.out 45 239 123 Average=135.666667 $

Passingparameterstomain()•  Twoparameterswillbepassedtofunchonmain()through

commandline–argcandargv.

•  Nameoftheparametersarefixed.

•  argcisofintegertypeanditstoresthenumberofparameters(delimitedbyspace)inthecommandline.

•  argvisa2Darrayofcharactersanditstoresallthewordsinthecommandline.

•  Bydefaultalltheparametersaretakenasarrayofcharacters(strings)thatcanbeconvertedtootherdatatypes.

FileHandling

AdvantagesofFilehandling

•  Athmessizeoftheprograminputisverylarge.

•  Duringtheteshngphaseprovidinginputsintheinterachvewayistedious.

•  Thesizeoftheprogramoutputmaybelargeenoughandwillnotfitinasinglescreen.

•  Youmaywishtostoretheoutputforfutureanalysis.

FilehandlinginC

•  Afileneedstobeopenedfirstforanyinput/outputoperahonsonthefile.–  Itmaybeopenedforreading/wrihng/appending.

•  Thefilemustbeclosedoncetheuse/handlingofthefileisover.

•  Inbetweentheaddressofthefilewillbestoredinapointerdatatypeviz.,FILE*.

FilehandlinginC

•  InCweuseFILE*torepresentapointertoafile.•  fopenisusedtoopenafile.ItreturnsapointertothefileifsuccessfullyopenedthefileelseitreturnsNULL.

FILE *fptr; char filename[]= "file2.dat"; fptr= fopen (filename,"w"); if (fptr == NULL) { printf (“ERROR IN FILE CREATION”); /* DO SOMETHING */ }

exit()funcJon•  Somehmeserrorcheckingmeanswewantan"emergencyexit"fromaprogram.Wewantittostopdead.

•  Inmainwecanuse"return"tostop.•  Infunchonswecanuseexittodothis.•  Libraryfilestdlib.histheheaderfileforexit()funchon.

FILE*fptr;charfilename[]="file2.dat";fptr=fopen(filename,"w");if(fptr==NULL){prin1(“ERRORINFILECREATION”);exit(-1);}

Modesforopeningfiles

•  Thesecondargumentoffopenisthemodeinwhichweopenthefile.

•  "r"opensafileforreading.

•  "w"createsafileforwrihng-andwritesoverallpreviouscontents(deletesthefilesobecareful!).

•  "a"opensafileforappending-wrihngontheendofthefile.

Closingafile

•  Wecancloseafilesimplyusingfclose()andthefilepointer.

FILE *fptr; char filename[]= "myfile.dat"; fptr= fopen (filename,"w"); if (fptr == NULL) { printf ("Cannot open file to write!\n"); exit(-1); } fprintf (fptr,"Hello World of filing!\n"); fclose (fptr);

Opening

Access

closing

WriJngtoafileusingfprin\()

•  fprin1()worksjustlikeprin1andsprin1exceptthatitsfirstargumentisafilepointer.

FILE *fptr; fptr= fopen ("file.dat","w"); /* Check it's open */ fprintf (fptr,"Hello World!\n");

ReadingDataUsingfscanf()

FILE*fptr;fptr=fopen(“input.dat”,“r”);/*Checkit'sopen*/if(fptr==NULL){prin1(“Errorinopeningfile\n”);}fscanf(fptr,“%d%d”,&x,&y);

20 30

input.dat

x=20 y=30

ReadinglinesfromafileusingWecanreadastringusingfgets().

FILE *fptr; char line [1000]; /* Open file and check it is open */ while (fgets(line,1000,fptr) != NULL) { printf ("Read line %s\n",line); }

fgets() takes 3 arguments, a string, a maximum number of characters to read and a file pointer. It returns NULL if there is an error (such as EOF).

Checkwhetheramatrixissymmetricornot–V1

#include<stdio.h>intReadMat(intmat[1000][1000]){inti,j,size;prin1(“Matrixsize?:\n");scanf("%d",&size);for(i=0;i<size;i++)for(j=0;j<size;j++)scanf("%d",&mat[i][j]);returnsize;}

intmain(){charsymm='y';inti,j,size,mat[1000][1000];size=ReadMat(mat);for(i=0;i<size;i++){for(j=i+1;j<size;j++){if(mat[i][j]!=mat[j][i])symm='n';break;}if(symm=='n')break;}if(symm=='y')prin1("SymmetrixMatrix\n");elseprin1("NotSymmetric");return0;}

Checkwhetheramatrixissymmetricornot–V2

#include<stdio.h>intReadMat(intmat[1000][1000]){inti,j,size;FILE*fp;fp=fopen("Matrix.txt","r");//prin1(“Matrixsize:\n");fscanf(fp,"%d",&size);for(i=0;i<size;i++)for(j=0;j<size;j++)fscanf(fp,"%d",&mat[i][j]);fclose(fp);returnsize;}

intmain(){charsymm='y';inti,j,size,mat[1000][1000];size=ReadMat(mat);for(i=0;i<size;i++){for(j=i+1;j<size;j++){if(mat[i][j]!=mat[j][i])symm='n';break;}if(symm=='n')break;}if(symm=='y')prin1("SymmetrixMatrix\n");elseprin1("NotSymmetric");return0;}

Checkwhetheramatrixissymmetricornot–V3

#include<stdio.h>intReadMat(intmat[1000][1000]){charfilename[100];inti,j,size;FILE*fp;scanf(“%s”,filename);fp=fopen(filename,"r");//prin1(“Matrixsize:\n");fscanf(fp,"%d",&size);for(i=0;i<size;i++)for(j=0;j<size;j++)fscanf(fp,"%d",&mat[i][j]);fclose(fp);returnsize;}

intmain(){charsymm='y';inti,j,size,mat[1000][1000];size=ReadMat(mat);for(i=0;i<size;i++){for(j=i+1;j<size;j++){if(mat[i][j]!=mat[j][i])symm='n';break;}if(symm=='n')break;}if(symm=='y')prin1("SymmetrixMatrix\n");elseprin1("NotSymmetric");return0;}

Checkwhetheramatrixissymmetricornot–V4

#include<stdio.h>intReadMat(charfilename,intmat[1000][1000]){inti,j,size;FILE*fp;fp=fopen(filename,"r");//prin1(“Matrixsize:\n");fscanf(fp,"%d",&size);for(i=0;i<size;i++)for(j=0;j<size;j++)fscanf(fp,"%d",&mat[i][j]);fclose(fp);returnsize;}

intmain(intargc,char*argv[]){charsymm='y';inti,j,size,mat[1000][1000];size=ReadMat(argv[1],mat);for(i=0;i<size;i++){for(j=i+1;j<size;j++){if(mat[i][j]!=mat[j][i])symm='n';break;}if(symm=='n')break;}if(symm=='y')prin1("SymmetrixMatrix\n");elseprin1("NotSymmetric");return0;}

BalancedSymbolChecking

Inprocessingprogramsandworkingwithcomputerlanguagestherearemanyinstanceswhensymbolsmustbebalanced{},[],()

WriteaprogramthatwilltakeaCprogramfileascommandlineinputandprintswhetheralltheparenthesis,curlyandsquarebracketsthatareopenedhasclosedornot.

BalancedSymbolCheckingwhile(line[i]!='\0'){switch(line[i]){case'(':pbracket++;break;case')':pbracket--;break;case'{':cbracket++;break;case'}':cbracket--;break;case'[':sbracket++;break;case']':sbracket--;break;}i++;}}fclose(fp);if(pbracket==0)prin1("ParentesisOpen-Close.\n");elseprin1("ParentesisMismatches.\n");if(cbracket==0)prin1("CurlyOpen-Close.\n");elseprin1("CurlyMismatches.\n");if(sbracket==0)prin1("SquareOpen-Close.\n");elseprin1("SquareMismatches.\n");return0;}

#include<stdio.h>#include<stdlib.h>intmain(intargc,char*argv[]){FILE*fp;charline[500];inti,pbracket,cbracket,sbracket;fp=fopen(argv[1],"r");if(fp==NULL){prin1("Fileopeningerror...exihng");exit(0);}pbracket=cbracket=sbracket=0;while(!feof(fp)){fgets(line,100,fp);i=0;

Didfileopenproperly?

Fileendisnotreached.

BalancedSymbolChecking

Inprocessingprogramsandworkingwithcomputerlanguagestherearemanyinstanceswhensymbolsmustbebalanced{},[],()

FollowingCsyntax: - {}[]()….isallowed - {[}]()…isnotallowed.

Algorithm:BalancedSymbolChecking

•  Makeanemptystack

•  Readcharactersunhlendoffile–  Ifasymbolisanopeningsymbolpushitontothestack–  Ifasymbolisaclosingsymbolpopthestack

•  ifthestackisemptyreportanerror•  ifthepoppedsymboldoesnotmatchtheclosingsymbolreportanerror

•  Ifthestackisemptyreportsymbolsarebalanced.

•  Elsereportanerror

HomeworkWriteaCprogramthatwilltakeanyCprogramascommandlineinputandwillreportanysyntaxerrorduetobalancinginbracketsymbols.

ThreespecialI/Ostreams

•  Threespecialfilestreamsaredefinedinthe<stdio.h>header

•  stdinreadsinputfromthekeyboard

•  stdoutsendoutputtothescreen

•  stderrprintserrorstoanerrordevice(usuallyalsothescreen)

•  Whatmightthisdo?

fprintf (stdout,"Hello World!\n");

Anexampleprogram#include<stdio.h>intmain(){ inti; fprin1(stdout,"Givevalueofi\n"); fscanf(stdin,"%d",&i); fprin1(stdout,"Valueofi=%d\n",i); fprin1(stderr,"Noerror:Butanexampletoshowerrormessage.\n");

return0;}$./a.outGivevalueofi15Valueofi=15Noerror:Butanexampletoshowerrormessage.$

Display on the screen

InputFile&OutputFileredirecJon

•  Onemayredirecttheinputandoutputfilestootherfiles(otherthanstdinandstdout).

•  Usage:Supposetheexecutablefileisa.out$ ./a.out <in.dat >out.dat

15

in.dat

Give value of i Value of i=15

out.dat

No error: But an example to show error message.

Display screen

Example1:Reverseastackusingrecursion

Youarenotallowedtouseloopconstructslikewhile,for..etc

Sampleinput:1234Sampleoutput:4321

4 3 2 1

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1 2 3 4

top

Example2:Sortastackusingrecursion

Youarenotallowedtouseloopconstructslikewhile,for..etc

Sampleinput:1418-530Sampleoutput: 301814-5

30 -5 18 14

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-5 14 18 30

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Example3:ImplementaJonofMergingoperaJoninMergeSortusing

Stacks

-9 -3 56 90

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-5 14 18 30

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18 30 56 90

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-9 -5 -3 14

Example4:Givenastack,printtheNextGreaterElement(NGE)foreveryelement.

•  Foranystackthebo}ommostelementalwayshasnextgreaterelementas-1

•  Forastackwhichissortedindecreasingorder,allelementshavenextgreaterelementas-1.

•  Fortheinputstack[4,5,2,25],thenextgreaterelementsforeachelementareasfollows.

•  Element NGE4 55 252 2525 -1

Example5:ImplementaStackusingaLinkedList

-9 -3 56 90

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90 56 -3 -9

head

Example6:PrintfirstNFibonacciNumbersusingaQueue

Thequeueinihallycontains0and1

1 0

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Example7:UseaStacktoreverseaQueue

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14 18 -5 30

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Example 8: Create a newQueuewith givenelementsappendedattheendoftheQueueinareverseorder

*Hint-Youcanuseastackinordertoachievetheoutcome

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14 18 -5 30

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Example9:ImplementaStackusingaQueuedatastructure

ForagivenstackcreateasamesizearraywhichyouaregoingtouseasaQueue.

Pushandpopoperahonofstack’sshouldbeemulatedwiththeEnqueueandDequeueoperahon.

YoucanuseanintermediateQueuefortheaboveimplementahon.

Example10:ImplementaQueueusingaLinkedList

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