链表的奇偶排序

将级数位的排在前面，偶数位的排到后面，。

利用两个指针，可以完成这个。

 

/**
* 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==NULL) return NULL;

ListNode* odd = head;
ListNode* even = head->next;
ListNode* evenlist = even;
if(head!=NULL){
while(even!=NULL&&even->next!=NULL){
odd->next = odd->next->next;
even->next = even->next->next;
odd = odd->next;
even = even->next;
}
odd->next = evenlist;
}
return head;

}
};