用C语言编写一串代码，将两个升序的头指针型单链表合并为降序的头指针单链表

#include <stdio.h>
#include <stdlib.h>

typedef struct Node{
    int data;
    struct Node *next;
}Node, *pNode;

pNode mergeList(pNode head1, pNode head2) {
    pNode head3 = NULL, p = NULL;
    while (head1 != NULL && head2 != NULL) {
        if (head1->data >= head2->data) {
            //头插法
            pNode tmp = head1;
            head1 = head1->next;
            tmp->next = NULL;
            if (head3 == NULL) {
                head3 = tmp;
                p = tmp;
            } else {
                tmp->next = head3;
                head3 = tmp;
            }
        } else {
            //同上
            pNode tmp = head2;
            head2 = head2->next;
            tmp->next = NULL;
            if (head3 == NULL) {
                head3 = tmp;
                p = tmp;
            } else {
                tmp->next = head3;
                head3 = tmp;
            }
        }
    }
    //剩余的节点都连到 head3 的开头
    while (head1 != NULL) {
        pNode tmp = head1;
        head1 = head1->next;
        tmp->next = NULL;
        if (head3 == NULL) {
            head3 = tmp;
            p = tmp;
        } else {
            tmp->next = head3;
            head3 = tmp;
        }
    }
    while (head2 != NULL) {
        pNode tmp = head2;
        head2 = head2->next;
        tmp->next = NULL;
        if (head3 == NULL) {
            head3 = tmp;
            p = tmp;
        } else {
            tmp->next = head3;
            head3 = tmp;
        }
    }
    return head3;
}

int main() {
    pNode p1 = (pNode)malloc(sizeof(Node));
    pNode p2 = (pNode)malloc(sizeof(Node));
    pNode p3 = (pNode)malloc(sizeof(Node));
    pNode p4 = (pNode)malloc(sizeof(Node));
    pNode p5 = (pNode)malloc(sizeof(Node));
    pNode p6 = (pNode)malloc(sizeof(Node));

    p1->data = 1; p1->next = p2;
    p2->data = 3; p2->next = p3;
    p3->data = 5; p3->next = NULL;

    p4->data = 2; p4->next = p5;
    p5->data = 4; p5->next = p6;
    p6->data = 6; p6->next = NULL;

    pNode head1 = p1, head2 = p4;

    printf("List1: ");
    while (head1 != NULL) {
        printf("%d ", head1->data);
        head1 = head1->next;
    }
    printf("\nList2: ");
    while (head2 != NULL) {
        printf("%d ", head2->data);
        head2 = head2->next;
    }

    pNode head3 = mergeList(p1, p4);

    printf("\nMerged list: ");
    while (head3 != NULL) {
        printf("%d ", head3->data);
        head3 = head3->next;
    }

    return 0;
}