Matematické Fórum

#define min(a,b) ((a)<(b) ? (a) : (b))

int is_member(int element, int *array, int array_length)
{
    int i;

    for (i = 0; i < array_length; i++) if (array[i] == element) return 1;

    return 0;
}

int nr_of_occur(int element, int *array, int array_length)
{
    int i, nr;

    nr = 0;
    for (i = 0; i < array_length; i++) if (array[i] == element) nr += 1;

    return nr;
}

void array_intersection(int *a1, int length_a1, int *a2, int length_a2, int *intersection, int *intersection_length)
{
    int i, j, nr;

    *intersection_length = 0;

    for (i = 0; i < length_a1; i++)
    {
        /* go through array a1 */

        if (!is_member(a1[i], intersection, *intersection_length))
        {
            /* a1[i] is not in the output array - compute a number of its occurance in input arrays */
            nr = min(nr_of_occur(a1[i], a1, length_a1), nr_of_occur(a1[i], a2, length_a2));

            /* add nr copies of a1[i] into the output array, and update its length */
            for (j = 0; j < nr; j++) intersection[*intersection_length++] = a1[i];
        }
    }
}

void main(void)
{
    int a1[100], length_a1;
    int a2[100], length_a2;
    int a3[100], length_a3;

    /* fill in a1, a2, length_a1, length_a2 */

    array_intersection(a1, length_a1, a2, length_a2, a3, &length_a3);

    /* work with a3 - valid length is length_a3 */
}