Exercise 2.05

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.)

#include <stdio.h>
#include <stdbool.h>

int any(char s1[], char s2[])
{
	int i, j, k;
	int num_unique;
	bool found;

	/* Reduce s2 to unique characters */
	for (i = num_unique = 0; s2[i] != '\0'; i++) {
		found = false;
		for (j = 0; j < num_unique; j++) {
			if (s2[j] == s2[i]) {
				found = true;
				break;
			}
		}

		if (!found) {
			s2[num_unique++] = s2[i];
		}
	}
	s2[num_unique] = '\0';

	/* Eliminate from s1 all found in s2 */
	for (i = j = 0; s1[i] != '\0'; i++) {
		found = false;
		for (k = 0; k < num_unique; k++) {
			if (s1[i] == s2[k]) {
				return i;
			}
		}
	}
	return -1;
}

int main()
{
	char s1[] = "abcdefg";
	char s2[] = "defghij";

	printf("%d", any(s1, s2));
}