876. Middle of the Linked List

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:

    int length(ListNode*& head){
        ListNode* temp = head;
        int cnt = 0;
        while(temp != NULL){
            cnt++;
            temp = temp -> next;
        }
        return cnt;
    }

    ListNode* middleNode(ListNode* head) {
        int n = length(head)/2;
        int cnt = 1;
        ListNode* temp = head;
        while(cnt <= n){
            cnt++;
            temp = temp -> next;
        }
        head = temp;

        return head;
    }
};