/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* middleNode(ListNode* head) {
        if(head == nullptr) {return nullptr;}
        ListNode* single = head;
        ListNode* jump = head;
        while(jump->next) {

            single = single->next;
            jump = jump->next;

            if(jump->next) {
                jump = jump->next;
            }
        }
        return single;
    }
};