Finding an array of characters in a string

Question

I've written some code that I believe is very close to the answer of the problem, but I can't seem to properly compare two characters. I don't know how to properly cast them.

I know how to do this using arrays, but I want to know how to do it using pointers.

char *FindToken(char *s,char *t)
{
    while (s)
    {
        //char check = *(char*)s; tried this but it doesn't work
        while(t)
        {
            if (strcmp(s,t)){
                //return s;
                printf("%s", s);
            }
            t++;
        }
        s++;
    }
    return NULL;
}

This is the original problem:

Write a C function called that accepts 2 parameters: a null terminated character array (string) called S in reference to the string to be searched, and a second string parameter called T. The string T is a list of characters (not including the ‘\0’) that are tokens, or characters to be searched for in S. Do not modify either S or T. It will return a character pointer to the position of the first character in T that is found in S, if it is found in S, or NULL otherwise.

For example:

printf("%s", *FindToken(“are exams over yet?”, “zypqt”)); // will display “yet?”

You probably can't use it, but this assignment is to write a version of the standard strpbrk() function, fwiw. — Shawn
– Shawn, Commented Apr 10, 2019 at 12:08

kiran Biradar · Accepted Answer · 2019-04-10 12:10:57Z

7

You were almost close.

With few problems.

When you do (t++), ultimately you are making t to point end of its memory and leading UB.
strcmp is not for comparing char as you wanted.

char *FindToken(char *s,char *t)
{
    while (*s)
    {
        int i = 0;
        //char check = *(char*)s; tried this but it doesn't work
        while(t[i])
        {
            if (*s == t[i])) {
                printf("%s", s);
                return s;
            }
            i++;
        }
        s++;
    }
    return NULL;
}

edited Apr 10, 2019 at 12:10

answered Apr 10, 2019 at 12:02

kiran Biradar

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1 Comment

kiran Biradar Over a year ago

@EdHeal Yes even little shorter :). But I've written some code that I believe is very close to the answer of the problem OP wanted to know his mistake in the current code only.

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