ASSIGNMENT PRESENTATION – 1 DATA STRUCTURES

TEAM-1

TOPIC: STRING- IMPLEMENTATION, OPERATIONS AND APPLICATIONS

TEAM MEMBERS: 1.ARUN KUMAR 2.DIVYA 3.GAYATHRI 4.KAVYA 5.MOHANA PRIYA 6.PRASHANTH

STRING: Finite sequence of characters. Data type storing sequence of data values, in

bytes according to character encoding. It is null terminated character array. Size of the

string is length of the string plus one. Variable is declared to have string data type,

holding some predetermined symbols. Represented using double quotes.Declaration: char name[size];Formal theory to represent strings: Let ∑ be a non-empty finite set of letters of an

alphabet. Elements of ∑ are called symbols or characters. A string over ∑ is any finite sequence of characters from ∑.

EG: if ∑={0,1} then 01101 is a string over ∑.

IMPLEMENTATION:String is a variable length array of characters

that is delimited by null character.They are implemented as array of bytes,

characters or code units in order to allow fast access to characters in a string.

Difference between character and string:String: character: char str[]=“H”; char str = ‘H’; H \0 H

1. Here H is a string not a character and they are enclosed by double quotes.

1. Here H is a character not a string and they are enclosed by single quotes.

2. They require two memory location including the null character.

2. It requires only single memory location and it doesn’t have null character.

Compiler assigns character string to a character array and automatically assigns a null character to the end of string.

size of the string= length of the string + 1. There are two types of strings namely:Mutable strings: Eg: C++, ruby. Immutable strings: Eg: Java, python.Reading strings: 1. Using scanf function. scanf(“%s”,str); 2. Using gets() function. gets(str); 3. Using getchar() and getche() funtion.

getchar(ch);Writing strings: 1. Using printf function. printf(“%s”,str); 2. Using gets() function. gets(str); 3. Using getchar() and getche() funtion.

getchar(ch);

Implementing strings using pointers:This uses a pointer to access the elements.

Eg: #include<stdio.h> void main() { char name[ ]=“hello”, *ptr; ptr=name; while(*ptr != ‘\0’) { printf(“%s”, *ptr); ptr++; } }Output: hello

OPERATIONS:Searching:

Searching is to find a particular character in a string or not and to return the position.

Algorithm: Search(A,N,VAL,POS) Step 1: [INITIALIZE] SET POS= -1 Step 2: [INITIALIZE] SET I=0 Step 3: Repeat Step 4 while I<N Step 4: IF A[I] = VAL SET POS = I PRINT POS Go to step 6. Step 5: PRINT “Value not present in the string” Step 6: EXIT.

Sorting:Sorting is used to arrange the characters in

an array using some order.Algorithm: SORTING(A,N) Step 1: Repeat Step 2 FOR I = 0 to N-1

Step 2: Repeat step 3 FOR J = 0 to N-1 Step 3: IF A[J]>A[I], then SWAP A[J] and A[J+1] [End of Inner and Outer Loop] Step 4: EXIT.Trim: String trim(String str);

Returns a string with whitespace stripped from the beginning and end of the string. Whitespace characters are \n,\t,\0 and plain space. It also has rtrim() and ltrim().

Insertion:The insertion operation inserts a string s, in

the main text T, at Kth position.Algorithm: INSERT(text,pos,str) Step 1: [INITIALIZE] SET I = 0, J = 0 and K=0

Step 2: Repeat step 3 to 4 while text[I] != ‘\0’ Step 3: If I=Pos, then Repeat while str[K] != ‘\0’ new_str[J]=str[K] SET J=J+1 and K=K+1 Else new_str[J] = text[I] SET J=J+1 Step 4: SET I = I+1 Step 5: SET new_str[J] = ‘\0’ Step 6: EXIT.

Deletion:It deletes a substring from a given text.

Algorithm: Step1: [INITIALIZE] SET I=0 AND J=0

Step 2: Repeat steps 3 to 6 while text[I] != ‘\0’ Step 3: If I = Pos, then Repeat step 4 while n>=0 SET I = 1+1

SET N=N-1 Step 4: SET new_str[J] = text[I] Step 5: SET J = J+1 Step 6: SET I = I+1 Step 7: SET new_str[J] = ‘\0’

Step 8: EXIT

String Manipulation Functions:1.The strcat function

Syntax: char *strcat(char *s1, char *s2);2.The strncat function

Syntax: char *strncat(char *s1, char *s2, size n);

3.The strchr functionSyntax: char *strchr(char *s1, int c);

4.The strrchr functionSyntax: char *strrchr(char *s1, int c);

5. The strcmp functionSyntax: char *strcmp(char *s1, char *s2);

6. The strncmp functionSyntax: char *strncmp(char *s1, char *s2,

size n);

7. The strcpy functionSyntax: char *strcpy(char *s1,char *s2);

8. The strncpy functionSyntax: char *strncpy( char *s1, char *s2,

size n);9. The strlen function

Syntax: int strlen(char *str);10. The strstr function

Syntax: char *strstr( char *s1, char *s2);11. The strspn function

Syntax: int strspn(char *s1, char *s2);12. The strcspn function

Syntax: int strcspn(char *s1, char *s2);13. The strpbrk function

Syntax: char *strpbrk( char *s1, char *s2);

14.The strtok functionSyntax: char *strtok( char *s1, char *delimiter);

15. The strtol functionSyntax: long strtol(char *str, char **end, int base);

16.The strtod functionSyntax: double strtod(char *str, char **end);

Program:#include<stdio.h>#include<string.h>int main()

{char str1[50]= “PROGRAMMING”, str2[50]= “IN C”, *pos;char s1[50]=“HELLO”, s2[50]=“HEY”, s3[10], *ptr;char delim[3]=“,”, str[50]=“HELLO, TO, THE, WORLD”;long num; double n;

strcat(str1,str2);

printf(“\n Using strcat function: %s”, str1);

strncat(str1,str2,2);

printf(“\n Using strncat function: %s”,str1);

pos= strchr(str1, ‘N’);

if(pos)

printf(“\n strchr- Character is found at position %d”, pos);

else

printf(“\n strchr- Character not found”);pos1= strrchr(str1,’M’);

if(pos1)

printf(“\n strrchr- last position of character is %d”, pos1);

else

printf(“\n strrchr- Character not found”);

if(strcmp(s1,s2)==0) printf(“\n strcmp- Strings are identical”);else printf(“\n strcmp- Strings are not identical”);if(strncmp(s1,s2,2)==0) printf(“\n strncmp- Strings are identical”);else

printf(“\n strncmp- Strings are not identical”);strcpy(s3,s1);printf(“\n strcpy function: %s”,s3);strncpy(s3,s1,2);printf(“\n strncpy function: %s”,s3);printf(“\n Length of the string: %d”,strlen(s1));

ptr=strstr(str1,str2); if(ptr) printf(“\n strstr- Substring found”);

else printf(“\n strstr- Substring not found”);printf(“\n strspn- Position of character that doesnot match: %d”, strspn(str1,str2));printf(“\n strcspn- Position of first character that matches: %d”, strspn(str1,str2));*ptr= strpbrk(str2,s3);if(ptr==NULL) printf(“\n strpbrk- No character matches using pointer”);else printf(“\n strpbrk- Character matches”);result=strtok(str, delim);

while(result != NULL){ printf(“\n strtok function: %s”,result); result= strtok(NULL,delim);}num= strtol(“65432 octal”, NULL, 8);printf(“strtol function: octal value is %ld”, num);n= strtod(“123.456abcd”,NULL);printf(“\n strtod function: %lf”,n);returen 0;

}Output:

Using strcat function: PROGRAMMING IN CUsing strncat function: PROGRAMMING INstrchr- Character is found at the position: 9

strrchr- Last position of character is: 7strcmp- Strings are not identicalstrncmp- Strings are identicalstrcpy funcion- HELLOstrncpy function- HElength of the string- 5strstr- Substring foundstrspn- Position of the string that doesnot match: 3.strcspn- position of the character that matches: 8.strpbrk- No characters matches using pointer.strtok function: HELLO TO THE WORLD.strtol function: Octal value is 27418.strtod function: 123.456000

APPLICATIONS USING STRING: 1. Pattern matching in computation biology.

2. Text editor, Digital library and search engine.

3. String matching through 2-Dimensional meshes

REFERENCES: Reema Thareja, “Programming in C”, Oxford

University press, 2011. http://en.wikipedia.org/wiki/string_operation http://www.stackoverflow.com/string

THANK YOU !!!