合並兩個升序鏈表為一個升序鏈表

typedef struct Node
{
    int Data;
    struct Node *Next;
}Node, *List;

List Merge(List L1, List L2)

{
    List t1, t2, Ptr, L;
    if (L1 == NULL && L2 == NULL)
        return NULL;
    else if (L1 == NULL)
        return L2;
    else if (L2 == NULL)
        return L1;

    t1 = L1->Next;//指向第一個節點
    t2 = L2->Next;

    //構造一個帶頭結點的空鏈表
    L = (List)malloc(sizeof(struct Node));
    L->Next = NULL;

    Ptr = L;//指向新鏈表的頭節點

    while (t1 && t2)
    {
        if (t1->Data <= t2->Data)//比較兩個鏈表的值 將較小的加入新鏈表
        {
            Ptr->Next = t1;
            Ptr = t1;

            t1 = t1->Next;
            Ptr->Next = NULL;

        }
        else
        {
            Ptr->Next = t2;
            Ptr = t2;
            t2 = t2->Next;
            Ptr->Next = NULL;

        }
    }

    while (t1)
    {
        Ptr->Next = t1;
        Ptr = t1;
        t1 = t1->Next;
        Ptr->Next = NULL;

    }

    while (t2)
    {
        Ptr->Next = t2;
        Ptr = t2;
        t2 = t2->Next;
        Ptr->Next = NULL;

    }

    L1->Next = NULL;
    L2->Next = NULL;

    return L;
}