Poison

328. Odd Even Linked List

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class Solution {
public ListNode oddEvenList(ListNode head) {
ListNode dummyOddHead = new ListNode();
ListNode dummyEvenHead = new ListNode();
ListNode curr = head;

ListNode preOdd = dummyOddHead, preEven = dummyEvenHead;
while (curr != null) {
ListNode odd = curr;
ListNode even = curr.next; // even can be null

preOdd.next = odd;
preEven.next = even;

preOdd = odd;
preEven = even;

curr = even == null ? null : even.next;
}

preOdd.next = dummyEvenHead.next;

return dummyOddHead.next;
}
}
Reference

328. Odd Even Linked List