876.链表的中间结点 (Easy)*

class Solution {
public:
    ListNode* middleNode(ListNode* head) {
        // 跟回文那个差不多
        ListNode *slow = head, *fast = head;
        while(fast && fast->next) {
            fast = fast->next->next;
            slow = slow->next;
        }
        return slow;
    }
};