The C Programming Language ¾­µä´úÂë any(s1,s2)

/*
* Exercise 2-5 Page 48
*
* Write the function any(s1,s2), which returns the first location
* in the string s1 where any character from the string s2 occurs,
* or -1 if s1 contains no characters from s2. (The standard library
* function strpbrk does the same job but returns a pointer to the
* location.)
 
*
*/
Here's a much better solution, by Partha Seetala. This solution has a worst-
case time complexity of only O(n + m) which is considerably better.