/**  
 * 逆置单向链表  
 *  
 * @param headNode  
 * @return NormalListNode  
 * @author: Max Solider  
 * @date: 2022/10/9 14:18  
 */
 NormalListNode reverseList(NormalListNode headNode) {  
    if (headNode == null || headNode.getNext() == null) {  
        return headNode;  
    }  
    NormalListNode nextNode = null;  
    NormalListNode previousNode = null;  
    while (headNode != null) {  
        nextNode = headNode.getNext();  
        headNode.setNext(previousNode);  
        previousNode = headNode;  
        headNode = nextNode;  
    }  
    headNode = previousNode;  
    return headNode;  
}