C语言例程28：函數的返回值

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

int find_substr(char* s1, char* s2);

int main(int argc, char *argv[])
{
    if(find_substr("C is fun", "is") != -1)
        printf("Substring is found.\n");
    system("pause");
    return 0;
}

int find_substr(char* s1, char* s2)
{
    register int t;
    char *p, *p2;

    for(t = 0; s1[t]; t++)
    {
        p = &s1[t];
        p2 = s2;

        while(*p2 && *p2 == *p)
        {
            p++;
            p2++;
        }
        if(! *p2)
            return t;
    }
    return -1;
}