c - How do I complete K&R Exercise 2-4?

Question

I'm learning how to write programs in C using the k&r book (The C Programming Language) and I have a problem with one of the exercises. It's asking me to detect and remove a character in string s1, which matches any characters in the string s2.

So, say s1 = "A";

And s2 = "AABAACAADAAE"

I want it to return "BCDE"

I know I'm on the right path towards it, i just don't know how to design programs very well, could you give me any additional tips. I tried to read about the binary search tree algorithm, but felt it was a little too advanced for this mundane task.

Thanks everyone!

/* An alternate version of squeeze(s1, s2) that deletes each character in
 * s1 that matches any character in the string s2
 *
 * [email protected]
 */

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

void squeeze(char s[], char t[]);

char string[] = "BAD";
char sstring[] = "ABC";

int
main(void)
{
    squeeze(string, sstring);
    return 0;
}

void
squeeze(char s[], char t[])
{
    int i, j, d;

    d = 0;
    if(strstr(s, t) == NULL)
        printf("%c", s[i]);
    s[j] = '';
}

Answer 1

Great book. If I were you, I would proceed exactly as for the squeeze() in section 2.8, but instead of a direct comparison (s[i] != c) I would write and exploit a function

 int contains(char s[], int c)

which returns 1 if the string s contains c, 0 otherwise. Start with the simple approach; when it works you may improve performance with more complex solutions (binary search, but note that the problem doesn't require the characters in s2 to be in a particular order).