Question

Question 3: C-Strings and pointers (10 pts)

1. [5] The following function appends C-string str2, to C-string str1. Complete the function using array access, i.e. str1[i], but no pointer access.

Note: For both part a) and part b) you may not use any library function calls (e.g. you cannot use strlen, strcat, etc.)

// Append strt2 to str1

void my_strcat(char str1[], char str2[])

{

//YOUR CODE HERE  

}

// example of using my_strcat()

#include <stdio.h>

int main(void)

{

char my_str1[50] = “hello ”;

char my_str2[] = “world”;

my_strcat(my_str1, my_str2);

// Printf should print: hello world.

printf(“%s \n”, my_str1);

}

2. [5] Rewrite the above function, this time using pointer access, i.e. *str, but no array access.

Note: In general, a function’s parameter declarations “char str[]” and “char *str” are equivalent (i.e. they are interchangeable)

// Append strt2 to str1

void my_strcat(char* str1, char* str2)

{

// YOUR CODE HERE  

}

// example of using my_strcat()

#include <stdio.h>

int main(void)

{

char my_str1[50] = “hello ”;

char my_str2[] = “world”;

my_strcat(my_str1, my_str2);

// Printf should print: hello world.

printf(“%s \n”, my_str1);

}

Answer 1

a) [5] The following function appends C-string str2, to C-string str1. Complete the function using array access, i.e. str1[i], but no pointer access.

Ans.

#include <stdio.h>

void my_strcat(char str1[], char str2[])

{
   int c, d;

   c = 0;

    while (str1[c] != '\0') {// Run till str1 is complete
   c++;
    }

    d = 0;

    while (str2[d] != '\0') { // concate to str1
   str1[c] = str2[d];
   d++;
   c++;
   }

    str1[c] = '\0'; // add null to concate str1
}
int main(void)

{

char my_str1[50] = "hello " ;

char my_str2[] = "world";

my_strcat(my_str1, my_str2);

// Printf should print: hello world.

printf("%s \n", my_str1);

}

/* OUTPUT */

b) [5] Rewrite the above function, this time using pointer access, i.e. *str, but no array access.

ans.

#include <stdio.h>

void my_strcat(char* str1, char* str2)

{
   while(*str1)
str1++;

while(*str2)
{
*str1 = *str2;
str2++;
str1++;
}
*str1 = '\0';

}

int main(void)

{

char my_str1[50] = "hello " ;

char my_str2[] = "world";

my_strcat(my_str1, my_str2);

// Printf should print: hello world.

printf("%s \n", my_str1);

}

/* PLEASE UPVOTE */