7-51 两个有序链表序列的合并 (20 分)

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

typedef int ElemType;
typedef struct LNode{
    ElemType Data; /* 存储结点数据 */
    struct LNode *Next; /* 指向下一个结点的指针 */
}LNode, *LinkList; /* 定义单链表类型 */
LinkList Read(void);
LinkList Merge(LinkList La, LinkList Lb);
void Print(LinkList L);


int main()
{
    LinkList La, Lb, Lc;
    La = Read();
    Lb = Read();
    Lc = Merge(La, Lb);
    Print(Lc);

    return 0;
}
LinkList Read(void){ /* 读入链表元素，以-1位结束标志*/
    LinkList L,rear, temp;
    ElemType data;
    L = (LinkList)malloc(sizeof(LNode)); /* 链表头空结点*/
    L->Data = -1;
    L->Next = NULL;
    rear = L;
    scanf("%d", &data);
    while(data!=-1){
        temp = (LinkList)malloc(sizeof(LNode));
        temp->Data = data;
        //printf("Write:%d\n", temp->Data);
        temp->Next = NULL;
        rear->Next = temp;
        rear = rear->Next;
        scanf("%d", &data);
    }
    return L; /* 返回带头空结点的链表 */
}

LinkList Merge(LinkList La, LinkList Lb){
    /* 输入两个有序链表的头指针，返回合并后有序链表的头指针*/
    LinkList L, pa, pb, rear;
    L = (LinkList)malloc(sizeof(LNode));
    L->Data = -1;
    L->Next = NULL;
    rear = L; /* 尾插法，rear初始指向头结点*/
    pa = La->Next;
    pb = Lb->Next;
    //printf("Start Merging...\n");
    while(pa&&pb){
        if(pa->Data < pb->Data){
            rear->Next = pa;
            //printf("Get:%d\n", pa->Data);
            pa = pa->Next;
        }
        else{
            rear->Next = pb;
            //printf("Get:%d\n", pb->Data);
            pb = pb->Next;
        }
        rear = rear->Next;
    }
    while(pa){
        rear->Next = pa;
        //printf("Get:%d\n", pa->Data);
        pa = pa->Next;
        rear = rear->Next;
    }
    while(pb){
        rear->Next = pb;
        //printf("Get:%d\n", pb->Data);
        pb = pb->Next;
        rear = rear->Next;
    }
    rear->Next = NULL;
    /* 不删除原链表的头结点*/
    return L;
}

void Print(LinkList L){
    LinkList p;
    int tag = 1;
    p = L->Next;
    while(p){
        if(tag){ /* 第一个元素前面不带空格*/
            printf("%d", p->Data);
            tag = 0;
            p = p->Next;
        }
        else{
            printf(" %d", p->Data);
            p = p->Next;
        }
    }
    if(tag){
        printf("NULL");
    }
}