UNIT 2 STRINGS. Marks - 7

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1 1 UNIT 2 STRINGS Marks - 7

2 SYLLABUS 2.1 String representation : Reading and Writing Strings 2.2 String operations : Finding length of a string, Converting Characters of a string into upper case and lower case, Concatenation of two strings to form a new string, Appending, Reversing a string, Copying a string, Comparing strings, Insertion, Substring, Deletion 2

3 STRINGS String is defined as a sequence of characters. In terms of c language string is an array of characters. While storing the string in character array the size of the array must be one more then the size of the string. Because the last character in the string is \0 or NULL. The string terminated with NULL or \0 is known as null terminated string. For example: To store HELLO in array the array must be declared as char a[5]. For example: String HELLO is stored as shown in fig 3 H E L L O \0

4 String Character set: Lower case: a to z Upper case: A to Z Number: 0 to 9 Special Characters: + - * % / ( ) [ ] { } $ # &,.? Etc. Now we can assign a value to the string as char name[10]= ketan OR char name[10]={ k, e, t, a, n, \0 }; For Dynamic allocation we use, gets(string name); OR scanf( %s, string name); Example: gets(name); OR scanf( %s,name); puts(name); OR printf( %s,name); 4

5 STRING OPERATIONS Finding length of a string, Converting Characters of a string into upper case and lower case, Concatenation of two strings to form a new string, Appending, Reversing a string, Copying a string, Comparing strings, Insertion, Substring, Deletion 5

6 FINDING THE LENGTH OF STRING [STRLEN(STR)] This function finds the length of the string. str is the string whose length is to be find Example: char str[20]={ VPMP POLYTECHNIC }; int len; len=strlen(str); printf( String length = %d,len); Output: String length = 16 6

7 ALGORITHM [STRLEN(STR)] STEP 1: [initialize] len 0 STEP 2: [Process until end of the string] Repeat step 3 until str!=null STEP 3: [increment counter] str str+1 len len + 1 STEP 4: [Display Length] Write len STEP 5:[Finished] Exit 7

8 CONVERT THE CASE OF STRING: STRLWR(STR) This function is used to convert the case of string from uppercase to lowercase. Example: Output: char str[20]={ VPMP POLYTECHNIC }; printf( Lower case String = %s,strlwr(str)); Lower case String = vpmp polytechnic Algorithm STEP 1 STEP 2 [Initialization] i 0 len strlen(str) repeat upto step 5 while (i<len) 8

9 STEP 3 STEP 4 STEP 5 STEP 6 [ convert the case of string] if (STR[i]>=65 and STR[i]<=90) then STR[i] STR[i] + 32 else STR[i] STR[i] [Increment the counter] i i + 1 [Display string] Write STR [Finished] Exit 9

10 CONVERT THE CASE OF STRING: STRUPR(STR) This function is used to convert the case of string from lowercase to uppercase. Example: Output: char str[20]={ Vpmp Polytechnic }; printf( Uppercase String = %s,strupr(str)); Uppercase String = VPMP POLYTECHNIC Algorithm STEP 1 STEP 2 [Initialization] i 0 len strlen(str) repeat upto step 5 while (i<len) 10

11 STEP 3 STEP 4 STEP 5 STEP 6 [ convert the case of string] if (STR[i]>=97 and STR[i]<=122) then STR[i] STR[i] - 32 else STR[i] STR[i] [Increment the counter] i i + 1 [Display string] Write STR [Finished] Exit 11

12 CONCATENATION OF TWO STRINGS TO FORM A NEW STRING : STRCAT(S1,S2,S3) This function concatenate two strings s1 and s2 in to the string s3. Example: Output: char s1[5]={ vpmp }; char s2[15]={ polytechnic }; char s2[20]; strcat(s1,s2,s3); printf( s3 = %s,s3); s3= vpmppolytechnic 12

13 Algorithm STEP 1: [initialize] i 0 j 0 k 0 STEP 2: [process until end of first string] Repeat step 3 until s1 [i]!=null STEP 3: [copy character by character and increment counter] s3 [k] s1 [i] i i+1 k k+1 STEP 4: [process until end of first string] Repeat step 3 until s2 [j]!=null 13

14 STEP 5: [copy character by character and increment counter] s3 [k] s2 [j] j j+1 k k+1 STEP 6: [finish] Exit s3 [k] NULL 14

15 APPENDING This function append one string at the end of another string. Example: char s1[5]={ vpmp }; char s2[15]={ polytechnic }; strcat(s1,s2); printf( s1 = %s,s1); Output: s1=vpmppolytechnic Algorithm STEP 1: [initialize] i 0 j 0 15

16 STEP 2: [process until end of first string] Repeat step 3 until s2 [i]!=null STEP 3: [copy character by character and increment counter] STEP 4: [finish] s1 [j] s2 [i] i i+1 j j+1 s1 [j] NULL Exit 16

17 REVERSE A STRING This function is used to reverse the given string. Example: char str[10]={ vpmp }; printf( Reverse string = %s,strrev(str)); Output: Reverse string = pmpv Algorithm: STEP 1:[find the length of string] l strlen(str1) STEP 2: [Initialization] i l - 1 j 0 17

18 STEP 3: [Copy the string] Repeat while <i>=0) STR2[j] STR1[i] j j + 1 i i - 1 STEP 4: [Display string] STR2[j] null Write (STR2) STEP 5: [Finished] Exit 18

19 COPYING A STRING [STRCPY(STR1,STR2)] This function copies the string source in to the string destination. Example: Output: char str1[10]; char str2[10]={ vpmp }; strcpy(str1,str2); printf( Str1= %s,str1); Str1=vpmp 19

20 ALGORITHM STEP 1: [initialize] i 0 STEP 2: [Find the length of string] l strlen(str2) STEP 3: [copy character by character] repeat while (i<>l) STR1[i] STr2[i] i i+1 STEP 4: [Display string] STR1 [i] NULL write STR1 STEP 5: [Finished] Exit 20

21 COMPARING STRINGS This function compare two strings s1 and s2 and find weather they are equal or not. Example: char s1[10]={ VPMP }; char s2[10]={ VPmP }; if(strcmp(s1,s2)==0) { printf( Both are same ); } else { printf( Both are different ); } Output: 21 Both are different

22 Algorithm: STEP 1: [initialize] i 0 flag 0 STEP 2: [Find Length of two strings] L1 strlen (s1) L2 strlen (s2) STEP 3: [Compare Length of two string] if (L1!= L2) then Write Strings are not equal 22

23 STEP 4: [Process string] Repeat step 5 while i < L1 STEP 5: [compare character by character] If s1 [i]!=s2 [i] then flag 1 Else i i + 1 STEP 6: [Are string equal?] If flag == 0 then Write Strings are equal Else Write Strings are not equal STEP 7: [Finished] Exit 23

24 INSERTION This function is used to insert a string into existing string. Example: Output: char str[20]={ Gujarat University }; char new[15]={ Technological }; char temp[35]; INSERT(str,9,13); printf( Answer = %s,temp); Gujarat Technological University 24

25 Algorithm: INSERT(str, position,new) STEP 1: [Initialization] i 0 j 0 STEP 2: [Find the length of strings] l1 strlen(str) l2 strlen(new) STEP 3: [copy the characters upto position] repeat while (i<position) temp[i] str[i] i i+1 25

26 STEP 4: [copy the new string] repeat while (j<l2) temp[i] new[j] i i+1 j j+1 STEP 5: [copy the remaining characters] repeat while(position<l1) temp[i] str[position] i i+1 position position+1 STEP 6: [Display string] write temp STEP 7: [Finished] Exit 26

27 SUBSTRING [SUBSTR(STR,START,LEN)] This function finds the string sub string from the given string. Here START indicates the starting position in given string. LEN indicates number of character after starting position. Example: Output: char str[30]={ Gujarat Technological University }; printf( Answer = %s, substr(str,8,13)); Technological 27

28 Algorithm: SUBSTR(S1,START,LEN) STEP 1: [initialize] i 0 STEP 2: [Process the string] Repeat step 3 until LEN < 0 STEP 3: [Compare Length of two string] SUB[i] S1 [START] i i+1 START START+1 LEN LEN-1 STEP 4: [Finished] SUB[i] NULL 28

29 DELETION This function is used to delete a string from existing string. Example: char str[30]={ Gujarat Technological University }; char new[20]; printf( Answer = %s, delete(str,9,13); Output: Gujarat University 29

30 Algorithm: DELETE(str, position,n) STEP 1: [Initialization] i 0 STEP 2: [Find the length of strings] l strlen(str) STEP 3: [copy the characters upto position] repeat while (i<position) temp[i] str[i] i i+1 STEP 4: j position+n 30

31 STEP 5: [copy the remaining characters] repeat while(j<l) temp[i] str[j] i i+1 j j+1 STEP 6: [Display string] write temp STEP 7: [Finished] Exit 31

32 END 32

7.STRINGS. Data Structure Management (330701) 1

7.STRINGS. Data Structure Management (330701) 1 Strings and their representation String is defined as a sequence of characters. 7.STRINGS In terms of c language string is an array of characters. While storing the string in character array the size of