Function cmp_points

contents/graham_scan/code/c/graham.c:11–22

};

int cmp_points(const void *a, const void *b) {
    struct point* pa = (struct point*) a;
    struct point* pb = (struct point*) b;

    if (pa->y > pb->y) {
        return 1;
    } else if (pa->y < pb->y) {
        return -1;
    } else {
        return 0;
    }
}

double ccw(struct point a, struct point b, struct point c) {
    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);