[leetcode] 328. Odd Even Linked List 解题报告

题目链接：https://leetcode.com/problems/odd-even-linked-list/

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.

You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.

Example:
Given 1->2->3->4->5->NULL,
return 1->3->5->2->4->NULL.

Note:
The relative order inside both the even and odd groups should remain as it was in the input. 
The first node is considered odd, the second node even and so on ...

思路：这种链表的题目一般都都可以做出来，但是想要写的比较优雅还是要费些功夫。

代码如下：

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* oddEvenList(ListNode* head) {        if(!head || !head->next) return head;        ListNode *even = head->next, *p = even, *q = head;        while(p && p->next)        {            q->next = p->next;            q = q->next;            p->next = q->next;            p = p->next;        }        q->next = even;        return head;    }};