#include <stdio.h>

struct ListNode {
    int val;
    struct ListNode *next;
};

struct ListNode* middleNode(struct ListNode*);
struct ListNode* middleNode(struct ListNode* head){
    struct ListNode* ind = head;
    struct ListNode* middle = head;
    int on = 0;
    while (ind != NULL) {
        ind = ind->next;
        if (on == 0) {
            on = 1;
        } else {
            on = 0;
            middle = middle->next;
        }
    }
    return middle;
}

int main() {
    printf("Expected: [4, 5, 6]\n");
    printf("Got:");
    struct ListNode l6 = { 6, NULL };
    struct ListNode l5 = { 5, &l6 };
    struct ListNode l4 = { 4, &l5 };
    struct ListNode l3 = { 3, &l4 };
    struct ListNode l2 = { 2, &l3 };
    struct ListNode linkedList = { 1, &l2 }; 
    struct ListNode* middle = middleNode(&linkedList);
    while (middle != NULL) {
        printf(" %d ", middle->val);
        middle = middle->next;
    }
    printf("\n");
    return 0;
}