Tutorial: Strings Programming Assignments CS19001: Programming and Data Structures Laboratory

CS19001: Programming and Data Structures Laboratory

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

02-09-14

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Table of Contents

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings

1

Tutorial: Strings

2

Programming Assignments

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Table of Contents

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings

1

Tutorial: Strings

2

Programming Assignments

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Strings In C, a string is defined to be a null-terminated character array. The null character ’\0’ is used to indicate the end of the string. int main () { char greet [3]={ ’H ’ , ’i ’ , ’ \0 ’ }; printf ( " Greeting message : % s \ n " , greet ); return 0; }

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

Variation in initialization char char char char

c []= " abcd " ; c [5]= " abcd " ; c []={ ’a ’ , ’b ’ , ’c ’ , ’d ’ , ’ \0 ’ }; c [5]={ ’a ’ , ’b ’ , ’c ’ , ’d ’ , ’ \0 ’ }; Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments CS19001: Programming and Data Structures Laboratory

Reading string from terminal # include < stdio .h > int main (){ char name [20]; printf ( " Enter name : " ); scanf ( " % s " , name ); printf ( " Your name is % s . " , name ); return 0; }

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

Enter name: Dennis Ritchie Your name is Dennis. scanf() function takes only string before the white space.

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments CS19001: Programming and Data Structures Laboratory

Reading a line of text int main (){ char name [30] , ch ; int i =0; printf ( " Enter name : " ); while ( ch != ’\ n ’) { // t e r m i n a t e s if user hit enter ch = getchar (); name [ i ]= ch ; i ++; } // i n s e r t i n g null c h a r a c t e r at end name [ i ]= ’ \0 ’; printf ( " Name : % s " , name ); return 0; } Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments CS19001: Programming and Data Structures Laboratory

Better method int main (){ char name [30]; printf ( " Enter name : " ); gets ( name ); // Function to read string from user . printf ( " Name : " ); puts ( name ); // Function to display string . return 0; }

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

Enter name: Dennis Ritchie Name: Dennis Ritchie

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments CS19001: Programming and Data Structures Laboratory

Passing Strings to Functions void Display ( char ch []); int main (){ char c [50]; printf ( " Enter string : " ); gets ( c ); Display ( c ); // Passing string c to function . return 0; } void Display ( char ch []){ printf ( " String Output : " ); puts ( ch ); }

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Library functions # include < stdio .h > # include < string .h > int main () { char str1 [12] = " Hello " ; char str2 [12] = " World " ; char str3 [12]; int len ; strcpy ( str3 , str1 ); printf ( " strcpy ( str3 , str1 ): % s \ n " , str3 ); strcat ( str1 , str2 ); printf ( " strcat ( str1 , str2 ): % s \ n " , str1 ); len = strlen ( str1 ); printf ( " strlen ( str1 ) : % d \ n " , len ); return 0; } Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Result

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings

strcpy( str3, str1) : Hello strcat( str1, str2): HelloWorld strlen(str1) : 10

Programming Assignments

do not forget to include string.h

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

A bit more about string manipulation

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

int strcmp (char s[], char t[]): Returns 0 if the two strings are identical, a negative value if s is lexicographically smaller than t (i.e., if s comes before t in the standard dictionary order), and a positive value if s is lexicographically larger than t. Comparison is done with respect to ASCII values (A - 65, a - 95)

Tutorial: Strings Programming Assignments

int strlen (char s[]): Returns the length (the number of characters before the first null character) of the string s.

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Table of Contents

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings

1

Tutorial: Strings

2

Programming Assignments

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Assignment 1: Complete and submit during lab Write a C program which reads three character strings str 1, str 2, and str 3 of size 20, 4 and 5 respectively and display the strings. 1

The program checks whether str 2 occurs in str 1 as a substring and in that case displays the starting index of all such occurrences.

2

The program replaces all occurrences of str 2 in str 1 by str 3 and displays the newly formed string. If that is not possible due to space limitation, then an appropriate message is printed.

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

[6]

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Assignment 2: Complete and submit during lab Write a C program which 1

declares two 1-d character arrays word[max size] and sentence[MAX SIZE], initialize integer variable ‘count’ to 0

2

asks the user to enter a string without intermediate white space (w say) and stores in word[max size]

3

asks the user to enter a sentence and stores in sentence[] (no. of char < MAX SIZE)

4

counts the frequency of w in sentence and adds up to ’count’. If the entered sentence is blank(\n is first character), then break. Else, goto step 3.

5

report the value of count.

Test run is given in next slide Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

[6] CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Assignment 2: Complete and submit during lab

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Enter word: algebra Enter sentence 1: algebra is boring (enter pressed) Enter sentence 2: Boolean algebra is part of syllabus (enter pressed) Enter sentence 3: (enter pressed) Frequency = 2

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Tutorial: Strings Programming Assignments

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Assignment 3: Complete and submit during lab Consider a string s1 = “abcadefbas” and a string s2 = “abc”. A prefix of s1 is any substring which starts from the first character of s1 . For example, “abc”, “ab”, “a”, “abcad” · · · are all prefixes of s1 . We are interested in finding the maximum length possible for a prefix of s1 such that all characters in the prefix are present in s2 . In our example with s1 and s2 , the maximum length is 4 for the prefix “abca” of s1 (the next character ’d’ is not present in s2 ). Write a C function

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

int max prefix(char s1[ ], char s2[ ]) where s1 and s2 contain null-terminated strings. The function returns the maximum length possible of a prefix of s1 with respect to s2 as defined above. [10] Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments

Assignment 4: Complete and submit during lab Write a C function void balance(int A[ ], int n, int k) which takes as parameter an array A with n elements and does the following: 1

Finds out whether the maximum of A[0] . . . A[k − 1] is greater than the minimum of A[k] . . . A[n − 1].

2

In case it is so, the function swaps the maxima and the minima and goes back to step (a).

3

In case it is not so, the function returns.

CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings Programming Assignments

Example run: Consider A = {12, 10, 20, 5, 6, 15} and the function call balance(A, 6, 3). A correct execution of balance() should ensure that A = {6, 10, 5, 20, 12, 15} after the function returns. [8] Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

CS19001: Programming and Data Structures Laboratory

Tutorial: Strings Programming Assignments CS19001: Programming and Data Structures Laboratory Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur Tutorial: Strings

Thank You

Soumyajit Dey, Rajib Mall CSE, IIT Kharagpur

Programming Assignments

CS19001: Programming and Data Structures Laboratory