题解 | #设计LRU缓存结构#

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    void reorderList(ListNode *head) {
        if(!head || !head->next) return;
        ListNode *fast=head->next, *slow=head;
        while(fast && fast->next) {
            slow = slow->next;
            fast = fast->next->next;
        }
        
        ListNode *worker = slow->next;
        slow->next = nullptr;
        while(worker) {
            ListNode *temp=worker->next;
            worker->next = slow->next;
            slow->next = worker;
            worker = temp;
        }
        
        ListNode *worker1=head, *worker2=slow->next;
        slow->next = nullptr;
        while(worker2) {
            ListNode *temp = worker2->next;
            worker2->next = worker1->next;
            worker1->next = worker2;
            worker1 = worker2->next;
            worker2 = temp;
        }
    }
};