Sprawdzanie podciągu w tablicy

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

int amount_substring(const char* where, const char* what)
{
    int i, amount = 0;
    int is;
    while (where != '\0')
        is = 1;
        for (i = 0; i < strlen(what); ++i) {
            *where++ == what[i] ? is = 1 : is = 0; // co jest nie tak z tą instrukcją
            if (is == 0)
                break;
        }

    return amount;
}

int main()
{
    char substring[] = { "tak" };
    char Fullstr[] = "tak,tak,nie";
    amount_substring(Fullstr, substring);
    return 0;
}

is = (*where++ == what[i]) ? 1 : 0;

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

int amount_substring(const char* where, const char* what)
{
    int i, amount = 0;
    int is;
    while (*where != '\0'){
        is = 1;
        for (i = 0; i < strlen(what); ++i) {
            is = (*where++ == what[i]) ? 1 : 0;
            if (is == 0)
                break;
            if(i == strlen(what)) ++amount;
        }
    }
    return amount;
}

int main()
{
    char substring[] = { "tak" };
    char Fullstr[] = "tak,tak,nie";
    printf("%d",amount_substring(Fullstr, substring));
    return 0;
}

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

int amount_substring(const char* where, const char* what)
{
    int i, amount = 0;
    int is;
    if(strlen(where) < strlen(what)) return 0;
    while (*where){
        is = 1;
        for (i = 0; i < strlen(what); ++i) {
            is = (*where++ == *(what+i)) ? 1 : 0;
            if (is == 0)
                break;
            if(i == strlen(what - 1)) ++amount;
        }
    }
    return amount;
}

int main()
{
    char substring[] = { "tak" };
    char Fullstr[] = "ta";
    printf("%d",amount_substring(Fullstr, substring));
    return 0;
}

int amount_substring(const char* where, const char* what)
{
    int result = 0;
    assert(where);
    assert(what);

    while (where && *where) {
          where = strstr(where, what);
          if (where) {
               ++where;
               ++result;
          }
    }
    return result;
}