/**  
 * 交换链表中的相邻结点  
 *  
 * @param headNode  
 * @return org.example.linkedlist.normal.NormalListNode  
 * @author: Max Solider  
 * @date: 2022/10/12 23:39  
 */
 NormalListNode exchangeAdjacentNodes(NormalListNode headNode) {  
    if (headNode == null || headNode.getNext() == null) {  
        return headNode;  
    }  
    NormalListNode current = headNode;  
    headNode = current.getNext();  
    while (current != null && current.getNext() != null) {  
        NormalListNode next = current.getNext();  
        // 逐对进行交换  
        NormalListNode temp = next.getNext();  
        next.setNext(current);  
        // 需要注意链表结点奇偶性  
        if (temp != null && temp.getNext() != null) {  
            current.setNext(temp.getNext());  
        } else {  
            current.setNext(temp);  
        }  
        current = temp;  
    }  
    return headNode;  
}