Reorder List [LeetCode]

Given a singly linked list L: L0→L1→…→Ln-1→Ln,
reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…

You must do this in-place without altering the nodes' values.

For example,
Given {1,2,3,4}, reorder it to {1,4,2,3}.

Solution: make sure the last element points to NULL in the new list;

 1     void reorderList(ListNode *head) {
 2         vector<ListNode * > nodes;
 3         ListNode * current = head;
 4         while(current != NULL) {
 5             nodes.push_back(current);
 6             current = current->next;
 7         }
 8         for(int i = 0; i < nodes.size() / 2; i ++){
 9             int next = nodes.size() - 1 - i;
10             if(i < next){
11                 ListNode * tmp = nodes[i]->next;
12                 nodes[i]->next = nodes[next];
13                 nodes[next]->next = tmp;
14             }
15         }
16         if(nodes.size() > 0)
17             nodes[nodes.size() / 2]->next = NULL;
18     }

 1     void reorderList(ListNode *head) {
 2         vector<ListNode * > nodes;
 3         ListNode * current = head;
 4         while(current != NULL) {
 5             nodes.push_back(current);
 6             current = current->next;
 7         }
 8         for(int i = 0; i < nodes.size() / 2; i ++){
 9             if(i < nodes.size() - 1 - i){
10                 nodes[i]->next = nodes[nodes.size() - 1 - i];
11                 if(i + 1 < nodes.size() - 1 - i)
12                     nodes[nodes.size() - 1 - i]->next = nodes[i + 1];
13                 else
14                     nodes[nodes.size() - 1 - i]->next = NULL;
15             }
16         }
17         if(nodes.size() % 2 == 1)
18             nodes[nodes.size() / 2]->next = NULL;
19     }