public static void main(String[] args) {
        Node n6 = new Node(6);

        Node n5 = new Node(5);
        n5.next = n6;
        Node n4 = new Node(4);
        n4.next = n5;
        Node n3 = new Node(3);
        n3.next = n4;
        Node n2 = new Node(2);
        n2.next = n3;
        Node n1 
 
= new Node(1);
        n1.next = n2;


        Node tmp = new Test().exchangeNode2(n1);

        System.out.println(n1);
    }

    public Node exchangeNode2(Node head) {
        Node first = new Node(-1);

        first.next = head;

        Node curr = first;
        Node p1 = null;
        Node p2 
 
= null;
        Node p2Next = null;
        for (; curr.next != null && curr.next.next != null; ) {
            p1 = curr.next;
            p2 = p1.next;
            p2Next = p2.next;

            curr.next = p2;
            p2.next = p1;
            p1.next = p2Next;
            curr = p1;
        }

        
 
return first.next;
    }

結果：

1,2,3,4,5,6 -》2，1,4,3,6,5