用单链表实现两个链表递减合并，为什么合并是显示指针为空？

Question

#include<iostream>
using namespace std;
typedef struct LNode
{
    int data;
    struct LNode* next;
}LNode, * LinkList;
int CreateList_T(LinkList& L, int n)//尾插
{
    LNode* p,*q;
    L = new LNode;
    L->next = NULL;
    q = L;
    cout << "请输入数据：";
    for (int i = 0; i < n; i++)
    {
        p = new LNode;
        cin >> p->data;
        q->next = p;
        q = p;
    }
    return OK;
}
int ConnectList(LinkList& L1, LinkList& L2)
{
    LNode* p , * q ,*r = L1;
    p = new LNode; q = new LNode;
    p = L1->next; q = L2->next;
    while (p && q)
    {
        if (p->data<q->data)
        {
            r->next = p;
            r = r->next;
            p = p->next;
            continue;
        }
        if (p->data == q->data)
        {
            r->next = p;
            r = r->next;
            p = p->next;
            q = q->next; 
            continue;
        }
        if (p->data > q->data)
        {
            r->next = q;
            r = r->next;
            q = q->next;
            continue;
        }
    }
    r->next = p ? p : q;
    return OK;
}
int DispList(LinkList& L, int n)
{
    LNode* p;
    p = new LNode;
    p = L;
    cout << "输出数据：";
    for (int j = 0; j < n; j++)
    {
        p = p->next;
        cout << p->data << " ";
    }
    return OK;
}
int main()
{
    LinkList L3,L4;
    cout << "合并两个有序单链表："<<endl;
    cout << "输入有序表L3：";
    CreateList_T(L3, 5);
    cout << "输入有序表L4：";
    CreateList_T(L4, 4);
    ConnectList(L3, L4);
    cout << "两表递减合并：";
    DispList(L3, 9);
}

Answer 1

返回前加上q->next=NULL;

int CreateList_T(LinkList& L, int n)//尾插
{
    LNode* p,*q;
    L = new LNode;
    L->next = NULL;
    q = L;
    cout << "请输入数据：";
    for (int i = 0; i < n; i++)
    {
        p = new LNode;
        cin >> p->data;
        q->next = p;
        q = p;
    }
    q->next=NULL;
    return OK;
}