求解问题

请问一下大家一个课上的题目，想了好久，不晓得哪里错了，自己指针链表的基础太差了。。。 原题是这样的：将两个递增的有序链表合并为一个递增的有序链表，要求结果链表还使用原本两个链表的存储空间，不另外占用其他的存储空间。表中不允许有重复元素 我的想法是这样的：用双链表来操作，并且一直在list1中去操作，两个链表去比较，如果list2的元素比list1的元素大，就把list2的元素插入到list1比较的元素后，反之就插入到list1比较的元素前，但我的逻辑部分应该是没写错，但到要输出的时候就卡住了一小会，然后直接退出程序了，我又不是很会c语言编译器的debug，问题应该出在merge这个函数里。

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;

// 定义双链表节点结构
struct DNode {
    int data;
    struct DNode* prior;
    struct DNode* next;
};

// 初始化 创建一个新的双链表节点
struct DNode* createDNode(int data) {
    struct DNode* newNode = (struct DNode*)malloc(sizeof(struct DNode));//分配空间
    newNode->data = data;
    newNode->prior = NULL; //头节点
    newNode->next = NULL; //首元节点
    return newNode;
}

// 合并两个递增有序双链表
struct DNode* mergeSortedLists(struct DNode* list1, struct DNode* list2) {
    struct DNode dummy;
    dummy.prior = NULL;
    dummy.next = NULL;
    struct DNode* tail = &dummy;

    while (list1 != NULL && list2 != NULL) {
        if (list1->data < list2->data) {//list1的元素小于list2的元素情况
            tail->next = list1; //新链表的首元指向小的
            list1->prior = tail; //完善链表
            list1 = list1->next; //当前元素比完，进一步
        } else if (list1->data > list2->data) {
            tail->next = list2; //同上
            list2->prior = tail;
            list2 = list2->next;
        } else { // 处理重复元素，传进去一个就行
            tail->next = list1;
            list1->prior = tail;
            list1 = list1->next;
            list2 = list2->next;
        }
        tail = tail->next; //走完后新链表进一步
    }
    //扫尾 如果有某一个链表中元素没加进去 直接加进去
    if (list1 != NULL) {
        tail->next = list1;
        list1->prior = tail;
    }

    if (list2 != NULL) {
        tail->next = list2;
        list2->prior = tail;
    }
    return dummy.next;
}
struct DNode* merge(struct DNode* list1, struct DNode* list2) {
    struct DNode* temp1 = list1;
    struct DNode* temp2 = list2;

    while (temp1 != NULL) {
        temp1->prior = NULL;
        temp1 = temp1->next;
    }

    // 遍历list2，确保prior指针为空
    while (temp2 != NULL) {
        temp2->prior = NULL;
        temp2 = temp2->next;
    }

    temp1 = list1;
    temp2 = list2; // 将temp2的赋值提到循环之前

    while (list1 != NULL && list2 != NULL) {
        if (list1->data < list2->data) {
            list2->prior = list1;
            list2->next = list1->next;
            list1->next->prior = list2;
            list1->next = list2;
            list1 = list1->next;
            temp2 = temp2->next; // 更新temp2指针
        } else if (list1->data > list2->data) {
            list2->next = list1;
            list2->prior = list1->prior;
            list1->prior->next = list2;
            list1->prior = list2;
            list1 = list1->next;
            temp2 = temp2->next; // 更新temp2指针
        } else {
            temp2 = temp2->next; // 处理重复元素，同时更新temp2指针
        }
    }

    // 扫尾 如果有某一个链表中元素没加进去 直接加进去
    if (list2 != NULL) {
        while (temp1->next != NULL) {
            temp1 = temp1->next;
        }
        temp1->next = list2;
        list2->prior = temp1;
    }

    return list1;
}


// 打印双链表
void printList(struct DNode* list) {
    struct DNode* current = list;//用临时指针代替以免指向混乱
    while (current != NULL) {
        printf("%d -> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

struct DNode* insert(struct DNode* list) {
    int n, data;
    // scanf("%d", &n);//链表长度
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> data;//第一个元素
        struct DNode* newNode = createDNode(data);
        if (list == NULL) {
            list = newNode;
        } else {
            struct DNode* temp = list;//临时指针
            while (temp -> next != NULL) {
                temp = temp -> next;//遍历直到指针末尾
            }
            temp -> next = newNode;//走完循环也就到了末尾
            newNode -> prior = temp;//前驱指针赋值
        }
    }
    return list;
}
int main() {
    struct DNode* list1 = NULL;
    struct DNode* list2 = NULL;

    list1 = insert(list1);
    list2 = insert(list2);

    cout << "the first list: ";
    printList(list1);
    cout << "the second list: ";
    printList(list2);

    // struct DNode* mergedList = mergeSortedLists(list1, list2);
    list1 = merge(list1, list2);
    cout << "merge list: ";
    printList(list1);

    // 释放链表节点的内存
    while (list1 != NULL) {
        struct DNode* temp = list1;
        list1 = list1->next;
        free(temp);
    }

    while (list2 != NULL) {
        struct DNode* temp = list2;
        list2 = list2->next;
        free(temp);
    }

    return 0;
}