关键点: 1.尾插法建立单链表  2.用两个指针去合并 

#include <iostream>
using namespace std;

struct ListNode
{
    int val;
    struct ListNode *next;
    ListNode(int value) : val(value), next(nullptr) {}
};

int main()
{
    int S1, S2;
    // 两个链表的虚拟头结点
    ListNode *phead1 = new ListNode(-1), *phead2 = new ListNode(-1);
    // 1.先建立两个链表
    ListNode *p, *r;
    cin >> S1;
    int val;
    r = phead1;
    for (int i = 0; i < S1; ++i)
    {
        cin >> val;
        ListNode *p = new ListNode(val);
        p->next = nullptr;
        r->next = p;
        r = p;
    }
    cin >> S2;
    r = phead2;
    for (int i = 0; i < S2; ++i)
    {
        cin >> val;
        ListNode *p = new ListNode(val);
        p->next = nullptr;
        r->next = p;
        r = p;
    }
    // 2.合并
    ListNode *p1 = phead1->next, *p2 = phead2->next;
    ListNode *phead3 = new ListNode(-1), *p3 = phead3;
    while (p...