LeetCode876. 链表的中间结点

这是小罗第一次在LeetCode上写的链表题呀！
先遍历一遍链表，然后得到链表的长度，返回中间结点

/**
 * 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:
    ListNode* middleNode(ListNode* head) {
        ListNode* p=head;
        ListNode* q=head;
        int k=0;
        while(p){
            p = p->next;
            k++;
        }
        int mid = k/2;
        int t = 0;
        while(t!=mid){
            q = q->next;
            t++;
        }
        return q;
    }
};