1. Reverse Linked List

2. Reverse Linked List II

3. Remove Nth Node From End of List

4. Remove Linked List Elements

5. Reorder List

Reverse Linked List, II, III

code template: reverse linked list

ListNode prev = null, curr = head;
while (curr != null) {
    ListNode temp = curr.next;
    curr.next = prev;
    prev = curr;
    curr = temp;
}
return prev;//prev is the new head with reverse linked list

4. Remove Linked List Elements

dummy + preDelete

注意下，没准要删除的元素是连续的，那种情况下不要动 preDelete node。就是要删去元素的时候，preDelete node不要动。