Solution to Cassido's interview question on Jan. 22, 2019 in C

repeat.c

/* Try It Online (TIO): https://bit.ly/2T9P9nq */

#include <stdio.h>

/*
step through the two character arrays, comparing character for character
when x is looped through, reset its position and increment the counter
when y is looped through, break the loop
before returning the counter, make sure that the loop finished both arrays, otherwise set the counter to -1
*/
int repeat(char** x, char** y) {
	int i = 0;
	int j = 0;
	int c = 0;
	while ((*y)[j] != '\0') {
		if ((*x)[i] == '\0') {
			i = 0;
		}
		if ((*x)[i] != (*y)[j]) {
			break;
		}
		j++;
		i++;
		c += ((*x)[i] == '\0') ? 1 : 0;
	}
	/* check to make sure both pointers are at the end of their strings */
	c = ((*x)[i] == '\0' && (*y)[j] == '\0') ? c : -1;
	return c;
}


/*
Expected output:
'pi', 'pipipi': 3
'wah', 'waluigi': -1
*/
int main() {
	char* a = "pi";
	char* b = "pipipi";
	printf("'%s', '%s': %d\n", a, b, repeat(&a, &b));
	char* c = "wah";
	char* d = "waluigi";
	printf("'%s', '%s': %d\n", c, d, repeat(&c, &d));
}