leetcode 328. Odd Even Linked List | 328. 奇偶链表（Java）

ゝ一世哀愁。 2023-01-23 08:55 122阅读 0赞

## 题目 ##

[https://leetcode.com/problems/odd-even-linked-list/][https_leetcode.com_problems_odd-even-linked-list]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

要注意的是，因为只将偶数位置的节点 append 到最后，所以用于判断停止的 tail 节点不一定是最后一个节点。这种情况下，不要遗失了 tail.next 节点。

class Solution { 
        public ListNode oddEvenList(ListNode head) { 
            if (head == null) return null;
            if (head.next == null || head.next.next == null) return head;
    
            ListNode tail = head;
            while (tail.next != null && tail.next.next != null) { 
                tail = tail.next.next;
            }
            ListNode newTail = tail;
            ListNode pre = head;
            ListNode cur = head.next;
            while (cur != tail) { 
                // cur 摘出来
                pre.next = cur.next;
                pre = pre.next;
                // cur 放到末尾
                cur.next = newTail.next;
                newTail.next = cur;
                newTail = cur;
                if (pre == tail) break;
                cur = pre.next;
            }
            return head;
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

[https_leetcode.com_problems_odd-even-linked-list]: https://leetcode.com/problems/odd-even-linked-list/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]: /images/20221004/f0df0f56f32749c8803fc23bef9aec9a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20221004/f0fc7892d8604538b28e4ebf17464480.png