/**  
 * 找到两个单向链表的合并点  
 *  
 * @param firstHeadNode  第一个链表的表头指针  
 * @param secondHeadNode 第二个链表的表头指针  
 * @return NormalListNode  
 * @author: Max Solider  
 * @date: 2022/10/9 14:18  
 */
 NormalListNode findIntersectingNode(NormalListNode firstHeadNode, NormalListNode secondHeadNode) {  
    if (firstHeadNode == null || secondHeadNode == null) {  
        return null;  
    }  
    // 计算两个链表的长度  
    int firstLength = getListLength(firstHeadNode);  
    int secondLength = getListLength(secondHeadNode);  
    // 计算两个链表的长度差值  
    NormalListNode longerNode = null;  
    NormalListNode shorterNode = null;  
    int diffLength = 0;  
    if (firstLength > secondLength) {  
        longerNode = firstHeadNode;  
        shorterNode = secondHeadNode;  
        diffLength = firstLength - secondLength;  
    } else {  
        longerNode = secondHeadNode;  
        shorterNode = firstHeadNode;  
        diffLength = secondLength - firstLength;  
    }  
    // 将指向更长链表的指针向前移动，直到两个指针距离合并点的距离相同  
    while (diffLength > 0) {  
        longerNode = longerNode.getNext();  
        diffLength--;  
    }  
    // 两个指针同时移动，相遇点即合并点。若没相遇则说明没有合并  
    while (longerNode != null) {  
        if (longerNode == shorterNode) {  
            System.out.println("The merging point of two linked lists is " + longerNode.getData());  
            return longerNode;  
        }  
        longerNode = longerNode.getNext();  
        shorterNode = shorterNode.getNext();  
    }  
    System.out.println("The is no merging point of two linked lists.");  
    return null;
}  

/**  
 * 计算链表长度  
 *  
 * @param headNode 链表头指针  
 * @return int 链表长度  
 * @author: Max Solider  
 * @date: 2022/10/9 16:36  
 */
 int getListLength(NormalListNode headNode) {  
    if (headNode == null) {  
        return 0;  
    }  
    int count = 0;  
    NormalListNode node = headNode;  
    while (node != null) {  
        node = node.getNext();  
        count++;  
    }  
    return count;  
}