1: Node[data: head, next node: null]
2: Node[data: tail, next node: null]
3: Node[data: head, next node: Node[data: tail, next node: null]]
4: Node[data: middle, next node: null]
5: Node[data: head, next node: Node[data: middle, next node: Node[data: tail, next node: null]]]
6: tail found: Node[data: tail, next node: null]