LeetCode 876. 链表的中间结点（快慢指针）

class Solution {
public:
    ListNode* middleNode(ListNode* head) {
        ListNode *fast = head, *slow = head;
        while(fast && fast->next)
        {
        	fast = fast->next->next;
        	slow = slow->next;
        }
        return slow;
    }
};