[LeetCode]Odd Even Linked List

这道题的基本思路就是，把奇数位置的节点连起来，偶数位置的节点连起来，最后merge起来即可。分别各用两个指针来track奇数链表和偶数链表的头尾节点，O(N)时间，常数空间。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* oHead = head, *eHead = head->next, *oCurr = oHead, *eCurr = eHead;
	while(eCurr->next)
	{
	oCurr->next = eCurr->next;
	oCurr = oCurr->next;
	if(!oCurr->next)break;
	eCurr->next = oCurr->next;
	eCurr = eCurr->next;
	}
	if(eCurr->next)eCurr->next = nullptr;
	if(oCurr->next)oCurr->next = nullptr;
	oCurr->next = eHead;
	return oHead;
	}
	};

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