合并两个链表从小到大输出（c++）

#include <iostream>
using namespace std;
typedef int ElementType;
typedef struct Node* PtrToNode;
struct Node {
	ElementType Data;
	PtrToNode   Next;
};
typedef PtrToNode List;

List Read(); /* 细节在此不表 */
void Print(List L); /* 细节在此不表；空链表将输出NULL */

List Merge(List L1, List L2);

int main()
{
	List L1, L2, L;
	
	L1 = Read();
	L2 = Read();
	
	L = Merge(L1, L2);
	
	Print(L);
	L1 = NULL;
	L2 = NULL;
	Print(L1);
	Print(L2);
	return 0;
}

List Read() {
	int n;
	cout << "请输入链表1结点个数" << endl;
	cin >> n;
	PtrToNode p = new Node;
	p->Next = NULL;
	PtrToNode head = p;
	ElementType x;
	while (n--) {
		PtrToNode tem = new Node;
		cin >> tem->Data;
		tem->Next = NULL;
		head->Next = tem;
		head = head->Next;
	}
	head->Next = NULL;
	PtrToNode t = p;
	p = p->Next;
	delete t;
	return p;
}

List Merge(List L1, List L2) {
	PtrToNode p, tem, head, t1, t2;
	t1 = L1;
	t2 = L2;
	p = new Node;
	p->Next = NULL;
	head = p;
	while (t1 && t2) {
		if (t1->Data >= t2->Data) {
			head->Next = t2;  //
			head = head->Next;
			t2 = t2->Next;
		}
		else{
			head->Next = t1;  //
			head = head->Next;
			t1 = t1->Next;
		}
	}
	head->Next = NULL;
    if(t1)
		head->Next = t1;  //
	else if (t2)
		head->Next = t2;  //
	tem= p;
	p = p->Next;
	delete tem;                                  //delete tem; 	p = p->Next;       卡在这卡了一个小时 如果先进行删除头指针指向
                                                                              //的结点，那后面的都没了
	
	return p;
}

void Print(List L) {
	if (L== NULL)
		cout << "null" << endl;
	else 
		while (L) {
			cout << L->Data << ends;
			L = L->Next;
		}
	cout << endl;
}