在C++中合并两个链表的问题

#include <iostream>

struct ListNode {
    int val;
    ListNode* next;
    ListNode(int x) : val(x), next(NULL) {}
};

ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
    ListNode* dummy = new ListNode(0); // 创建一个虚拟头节点
    ListNode* curr = dummy; // 当前节点指针

    while (l1 && l2) {
        if (l1->val < l2->val) {
            curr->next = l1;
            l1 = l1->next;
        } else {
            curr->next = l2;
            l2 = l2->next;
        }
        curr = curr->next;
    }

    // 将剩余的节点直接添加到新链表的末尾
    if (l1) {
        curr->next = l1;
    }
    if (l2) {
        curr->next = l2;
    }

    ListNode* result = dummy->next; // 获取合并后的链表
    delete dummy; // 释放虚拟头节点的内存
    return result;
}

int main() {
    // 创建链表1: 1 -> 2 -> 4
    ListNode* l1 = new ListNode(1);
    l1->next = new ListNode(2);
    l1->next->next = new ListNode(4);

    // 创建链表2: 1 -> 3 -> 4
    ListNode* l2 = new ListNode(1);
    l2->next = new ListNode(3);
    l2->next->next = new ListNode(4);

    // 合并两个链表
    ListNode* mergedList = mergeTwoLists(l1, l2);

    // 输出合并后的链表
    ListNode* curr = mergedList;
    while (curr) {
        std::cout << curr->val << " ";
        curr = curr->next;
    }
    std::cout << std::endl;

    // 释放链表的内存
    curr = mergedList;
    while (curr) {
        ListNode* temp = curr;
        curr = curr->next;
        delete temp;
    }

    return 0;
}