LeetCode OJ Reorder List

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}

.

class Solution {
public:
    void reorderList(ListNode *head) {
        if (head == NULL) {
            return;
        }
        int counter = 0;
        ListNode *move = head;
        while (move != NULL) {
            move = move->next;
            counter++;
        }
        ListNode* ln[counter];
        move = head;
        int i = 0;
        while (move != NULL) {
            ln[i++] = move;
            move = move->next;
        }
        int counter_2 = 0;
        int pos_1 = 0;
        int pos_2 = counter - 1;
        int h = 0;
        int t = counter - 1;
        int half = counter / 2;
        while (counter_2 < counter) {
            ln[pos_1]->next = ln[pos_2];
            pos_1 = pos_2;
            if (pos_2 > half) {
                h++;
                pos_2 = h;
            } else {
                t--;
                pos_2 = t;
            }
            counter_2++;
        }
        ln[half]->next = NULL;
    }
};