PTA：两个有序链表序列的交集-蒲公英云

PTA：两个有序链表序列的交集

已知两个非降序链表序列S1与S2，设计函数构造出S1与S2的交集新链表S3。
输入格式:
输入分两行，分别在每行给出由若干个正整数构成的非降序序列，用−1表示序列的结尾（−1不属于这个序列）。数字用空格间隔。
输出格式:
在一行中输出两个输入序列的交集序列，数字间用空格分开，结尾不能有多余空格；若新链表为空，输出NULL。

**输入样例:
1 2 5 -1
2 4 5 8 10 -1

输出样例:
2 5

#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
struct Node
{ 
    int number;
    Node *next;
};
typedef Node* ListNode;
Node* CreatList();                    //创建带空头结点的链表
Node* intersection(ListNode &a, ListNode &b); //取出两个链表数据中的交集
void PrintLsit(Node *p);              //打印链表
int main()
{ 
    Node *head1, *head2, *head;
    head1 = CreatList();
    head2 = CreatList();
    head = intersection(head1, head2);
    PrintLsit(head);
    return 0;
}
Node* CreatList()
{ 
    int temp;
    Node *head, *p, *tail;
    head = new(Node);
    head->next = NULL;
    tail = head;
    while (1)
    { 
        cin >> temp;
        if (temp == -1)
            break;
        p = new(Node);
        p->next = NULL;
        p->number = temp;
        tail->next = p;
        tail = p;
    }
    return head;
}
Node* intersection(ListNode &a, ListNode &b)
{ 
    Node *head, *p, *tail;
    head = new(Node);
    head->next = NULL;
    tail = head;
    a = a->next; b = b->next; 
    while (a != NULL && b != NULL)
    { 
        if (a->number > b->number)
            b = b->next;
        else if (a->number < b->number)
            a = a->next;
        else
        { 
            p = new(Node);
            p->next = NULL;
            p->number = a->number;
            a = a->next;
            b = b->next;
            tail->next = p;
            tail = p; 
        }
    }
    return head;
}
void PrintLsit(Node *p)
{ 
    p = p->next;
    if (p == NULL)
        cout << "NULL" << endl;
    if (p != NULL)
    { 
        cout << p->number;
        p = p->next;
    }
    while (p != NULL)
    { 
        cout << " " << p->number;
        p = p->next;
    }
}