/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* oddEvenList(ListNode* head) {
if(head==NULL){
return NULL;
}
if(head->next==NULL){
return head;
}
ListNode* odd = head;
ListNode* even_poi = head->next;
ListNode* even = head->next;
ListNode* curr = head;
curr = curr->next->next;
while(curr!=NULL and curr->next!=NULL){
odd->next = curr;
odd = odd->next;
even->next = curr->next;
even = even->next;
curr = curr->next->next;
}
if(curr!=NULL){
odd->next = curr;
odd = odd->next;
even->next = curr->next;
}
odd->next = even_poi;
return head;
}
};
