binary search on queue

/*
        Binary search on a queue. Complexity approaches 2*N (I think).
        Worse than linear search. I feel dirty now.
*/

#include <stdio.h>
#include <stdlib.h>

struct item {
        struct item *next;
        int mark;
        int x;
};

struct item *
make_list (int i, int x, int y)
{
        struct item *it = malloc(sizeof(struct item));
        
        it->mark = 0;
        
        if (0 == i) {
                it->next = NULL;
                it->x = x + y;
        } else {
                it->next = make_list(i - 1, y, x + y);
                it->x = x + y;
        }
        
        return it;
}

void
print_list (struct item *it)
{
        printf("%07d%c", it->x, it->mark ? '!' : ' ');
        
        if (NULL != it->next) {
                print_list(it->next);
        }
}

/* Use of goto instead of recursion, just to make it extra painful. */

void
search_list (const int g, struct item *start)
{
        struct item *lo = start, *hi, *slow = start, *fast = start;
        int ab = 1;
        
        while (NULL != fast->next) {
                fast = fast->next;
                if (ab ^= 1) {
                        slow = slow->next;
                }
        }
        
        if (slow->x >= g) {
                lo = start;
                hi = slow;
        } else {
                lo = slow;
                hi = fast;
        }
        
down:
        if (slow->next == fast) {
                goto end;
        }
        
        ab = 1;
        slow = fast = lo;
        while (hi != fast) {
                fast = fast->next;
                if (ab ^= 1) {
                        slow = slow->next;
                }
        }
        
        if (slow->x >= g) {
                hi = slow;
        } else {
                lo = slow;
                hi = fast;
        }
        
        goto down;
        
        
end:
        if (slow->x == g) {
                slow->mark = 1;
        }
        
        if (fast->x == g) {
                fast->mark = 1;
        }
}

int
main (void)
{
        struct item *it = make_list(29, 0, 1);
        
        print_list(it);
        printf("\nsearch for 610 ...\n");
        search_list(610, it);
        print_list(it);
        
        return EXIT_SUCCESS;
}