题目：

题解：

class Solution {
public:ListNode* oddEvenList(ListNode* head) {if (head == nullptr) {return head;}ListNode* evenHead = head->next;ListNode* odd = head;ListNode* even = evenHead;while (even != nullptr && even->next != nullptr) {odd->next = even->next;odd = odd->next;even->next = odd->next;even = even->next;}odd->next = evenHead;return head;}
};