Changing the size of an array

Question

Overall goal statement :

Your goal is to create a function that removes the first and last characters of a string. You're given one parameter, the original string. You don't have to worry with strings with less than two characters.

I have two arrays of the same size. if I want to remove the first and last element in the first array and add them to next array. suppose that I can't change the size of second array to (sizeof(firstarray) - 2) in the initial declaration;

if first array(string) is -

 char* array1[] = {"eloquent"};

and then the second array should be -

char* array2[] = {"loquen"};

I tried to do it and it does not work in some cases.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* remove_char(char* dst, const char* src)
{
  free(dst);
  dst = malloc(((int)sizeof(src) - 2));
  for (int i = 1; i < ((int)sizeof(src) - 1); i++)
    {
      dst[i - 1] = src[i];
  }
  /* src is the input string */
  /* your solution should write the result into dst and return it */
  return dst;
}

Answer 1

You are on the right track but you have a few problems.

• Do not free the pointer dst if you use it as an input parameter. You have to assume it's already been free'd or doesn't need to be or you will potentially introduce double free memory errors.

This assumes you can change the function signature

• Don't pass dst in at all only pass in the src, return dst.

• since you don't have to worry about strings with less than two characters if strlen(src) < 2 || sizeof(src) < 2 you can just return 0 (null) right away.

• while sizeof(src) would give you the size of the array you are forgetting that that size includes 1 or more null terminators*. Because of the nature of C you will need to employ both sizeof and strlen here. If strlen >= sizeof it isn't null terminated and this is a problem but not one I think they are going to force on you. In your main case strlen is how many characters you need to focus on in the loop and you will have to put the null terminator in manually. So you should malloc strlen(src)+1-2 as your size, +1 for null, -2 for removing two chars.

• your iteration range for the copying should then be over strlen-1 instead of size-1

• finally you should put dst[strlen(src)] = 0 to put the null terminator in place.

• note that technically they could give you 0 null terminators but for now I'm going to assume they arent that cruel because it would greatly complicate your logic. You should confirm what is fair game. Also note that they could give you multiple null terminators... your string input could be "foobar\0" which has 2 NULL's (i.e. char src[]="foobar\0"; where as char src[]="foobar" has 1 null, while char src[6]="foobar" has none)