[LeetCode] 328. Odd Even Linked List

 Problem : https://leetcode.com/problems/odd-even-linked-list/

Use dummy list to save odd and even node separately:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode oddEvenList(ListNode head) {
        ListNode odd = new ListNode();
        ListNode even = new ListNode();
        
        ListNode p = head;
        ListNode po = odd;
        ListNode pe = even;
        
        int count = 1;
        
        while (p != null) {
            if (count++ % 2 == 1) {
                po.next = p;
                po = po.next;
            } else {
                pe.next = p;
                pe = pe.next;
            }
            
            p = p.next;
        }
        
        po.next = even.next;
        pe.next = null;
        
        return odd.next;
    }
}

Edited on 12/01/2021. Replaced with iterative solution.