new listnode 280 29 meaning

1int size = 0;
2while (node != null) {
3    node = node.next;
4    size++;
5}

1node.val = node.next.val;
2node.next = node.next.next;

1ListNode dummy = new ListNode(0);
2dummy.next = head;

1ListNode fast = head;
2ListNode slow = head;
3
4while (fast != null && fast.next != null) {
5    slow = slow.next;
6    fast = fast.next.next;
7}