LinkedList:Given a linked list,

Given 1->2->3->4, you should return the list as 2->1->4->3.

public static ListNode swapPairs(ListNode head) {
        ListNode node = new ListNode(-1);
        node.next = head;
        ListNode cur = node;
        while (cur.next!=null&&cur.next.next!=null) {
            ListNode node1 = cur.next;
            ListNode node2 = cur.next.next;
            cur.next = node2;
            node1.next = node2.next;
            node2.next = node1;
            cur = node1;
        } 
        return node.next;
    }