两个递增单链表合并后变为递减链表

Question

#include <iostream>
#include<stdlib.h>
using namespace std;
#define max 100
typedef int element;
typedef struct sNode {
    element data ;
    struct sNode* next;
}node,*linkList ;
void initialList(node*&L ) {
    L = new node;
    L->next = NULL;
}
void listDecrease(node* A, node* B, node*& C) {
    node* pa, * pb,*u;
    pa = A->next;
    pb = B->next;
    while (pa != NULL && pb != NULL && pa->next != NULL && pb->next != NULL) {
        if (pa->data == pb->data) {
            //头插法
            u = new node;
            u->data = pa->data;
            u->next = C->next;
            C->next = u;
            pa = pa->next;
            pb = pb->next;
        }
        else if (pa->data < pb->data) {
            u = new node;
            u->data = pa->data;
            u->next = C->next;
            C->next = u;
            pa = pa->next;
        }
        else {
            u = new node;
            u->data = pb->data;
            u->next = C->next;
            C->next = u;
            pb= pb->next;
        }
    }
     
}
void listAdd(node* &L) {
    node* u,*R;
    R = L;
    element x;
    cout << "输入第一个元素(9999退出)：" << endl;
    cin >> x;
    while (x != 9999) {
        u = new node;
        u->data = x;
        u->next = NULL;
        R->next = u;
        R = u ;
        cout << "输入下一个元素(9999退出)：" << endl;
        cin >> x;
    }
}
void listPrint(node* L) {
    node* p = L->next;
    while (p != NULL) {
        cout << p->data;
        p = p->next;
    }
}
int main() {
    node* A, * B, * C;
    initialList(A);
    initialList(B);
    initialList(C);
    cout << "输入A中元素：" << endl;
    listAdd(A);
    cout << "输入B中元素：" << endl;
    listAdd(B);
    listDecrease(A, B, C);
    listPrint(C);
    return 0;
}

最后结果就是最大的两个数没有被写进C表，我知道是排除了pa->next = NULL或 pb->next = NULL的情况导致的但是要怎么处理才能把A,B表最后两个数写进去呢