02-线性结构1 两个有序链表序列的合并

本题要求实现一个函数，将两个链表表示的递增整数序列合并为一个非递减的整数序列。

函数接口定义：

List Merge( List L1, List L2 );

其中List结构定义如下：

typedef struct Node *PtrToNode;
struct Node {
    ElementType Data; /* 存储结点数据 */
    PtrToNode   Next; /* 指向下一个结点的指针 */
};
typedef PtrToNode List; /* 定义单链表类型 */

L1和L2是给定的带头结点的单链表，其结点存储的数据是递增有序的；函数Merge要将L1和L2合并为一个非递减的整数序列。应直接使用原序列中的结点，返回归并后的链表头指针。

本题自己测试了一上午了吧，在VS2013下是可以通过的，但是提交只是部分正确。

/*!
 * file 02-线性结构1 两个有序链表序列的合并.cpp
 *
 * author ranjiewen
 * date 2017/03/12 20:23
 *
 * 
 */

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

typedef int ElementType;
typedef struct Node *PtrToNode;
struct Node
{
    ElementType Data;
    PtrToNode Next;
}Node;

typedef PtrToNode List;  //定义单链表类型

List Read()
{
    printf("请输入一个链表的元素个数：
");
    int n = 0;
    scanf("%d", &n);

    List pHead = (List)malloc(sizeof(Node));
    List pCur = pHead;
    pCur->Next = NULL;
    if (pHead == NULL)
    {
        printf("pHead malloc faied!");
        exit(-1);
    }

    printf("请依次输入元素：
");
    int i, data = 0;
    for (i = 0; i < n; i++)
    {
        scanf("%d", &data);
        List pNode = (List)malloc(sizeof(Node));
        pNode->Data = data;
        pNode->Next = NULL;
        pCur->Next = pNode;
        //pCur++; 错误写法
        pCur = pNode; //移动当前节点到下一位置
    }
    return pHead;
}
void Print(List L) //空链表时输出null
{
    List pCur = L->Next;
    if (pCur == NULL)
    {
        printf("NULL");
    }
    while (pCur != NULL)//
    {
        printf("%d ", pCur->Data);
        pCur = pCur->Next;
    }
}

//L1和L2是给定的带头结点的单链表，其结点存储的数据是递增有序的；
//函数Merge要将L1和L2合并为一个非递减的整数序列。应直接使用原序列中的结点，返回归并后的链表头指针。
List Merge(List L1, List L2);
List Merge_(List L1, List L2);
int main()
{
    List L1, L2, L;
    L1 = Read();
    L2 = Read();
    L = Merge(L1, L2);
    Print(L);
    printf("
");
    L1->Next = NULL;
    L2->Next = NULL;
    Print(L1);
    printf("
");
    Print(L2);
    printf("
");
    return 0;
}

List Merge(List L1, List L2)
{
    List L;
    if (L1->Next == NULL)
    {
        L = L2;
        return L;
    }
    else if (L2->Next == NULL)
    {
        L = L1;
        return L;
    }

    List pCur1 = L1->Next;
    List pCur2 = L2->Next;

    while (pCur1!= NULL&&pCur2!= NULL) //
    {
        List pTemp, p1 = L1;
        while (pCur1->Data < pCur2->Data)
        {
            p1 = pCur1;   //记录当前结点之前的结点
            pCur1 = pCur1->Next;
            if (pCur1 == NULL||pCur2 == NULL)
            {
                break;
            }
        }
        pTemp = pCur2;
        pCur2 = pCur2->Next;
        pTemp->Next = pCur1;  //pTemp要插入pCur1之前
        p1->Next = pTemp;

        pCur1=L1->Next; //回到链表头             
    }

    if (pCur2 != NULL)
    {
        while (pCur1->Next)
        {
            pCur1 = pCur1->Next;
        }
        pCur1->Next = pCur2;
    }
    L = L1;
    return L;
}

List Merge_(List L1, List L2)
{
    List L=NULL;
    if (L1->Next==NULL )
    {
        return L2;
    }
    if (L2->Next==NULL)
    {
        return L1;
    }
    List pCur1 = L1->Next;
    List pCur2 = L2->Next;
    if (pCur1->Data<pCur2->Data)
    {
        L = pCur1;
        pCur1 = pCur1->Next;
    }
    else
    {
        L = pCur2;
        pCur2 = pCur2->Next;
    }

    List temp=L;
    while (pCur1&&pCur2)
    {
        if (pCur1->Data<pCur2->Data)
        {
            temp->Next = pCur1;
            pCur1 = pCur1->Next;
        }
        else
        {
            temp->Next = pCur2;
            pCur2 = pCur2->Next;
        }
        temp = temp->Next;
    }
    if (pCur1)
    {
        temp->Next = pCur1;
    }
    if (pCur2)
    {
        temp->Next = pCur2;
    }
    return L;
}  

测试结果：

很方。。。

等找到原因在更新了！

针对链表的操作，不同的方法难易程度不一样，我写了两种方法，其中第一种方法，很多坑，自己针对每种测试点都进行了修改；然后第二种方法应该和以前课本学的差不多；理解起来也简单。

 在网上找的这种写法可以过：

List Merge1(List L1, List L2){
    if (L1->Next == NULL){
        List temp, L;
        L = (List)malloc(sizeof(struct Node));
        temp = L2;
        L2 = L2->Next;
        L->Next = L2;
        while (L2){
            temp->Next = L2->Next;
            L2 = L2->Next;
        }
        return L;
    }
    else if (L2->Next == NULL){
        List temp, L;
        L = (List)malloc(sizeof(struct Node));
        temp = L1;
        L1 = L1->Next;
        L->Next = L1;
        while (L1){
            temp->Next = L1->Next;
            L1 = L1->Next;
        }
        return L;
    }
    else{
        List LL = (List)malloc(sizeof(struct Node));
        List LLL = LL;
        List temp1, temp2;
        temp1 = L1; 
        temp2 = L2;
        L1 = L1->Next; 
        L2 = L2->Next;
        while (L1 && L2){
            if (L1->Data < L2->Data){
                LL->Next = L1;
                LL = LL->Next;
                temp1->Next = L1->Next;
                L1 = L1->Next;
            }
            else{
                LL->Next = L2;
                LL = LL->Next;
                temp2->Next = L2->Next;
                L2 = L2->Next;
            }
        }
        while (L1){
            LL->Next = L1;
            LL = LL->Next;
            temp1->Next = L1->Next;
            L1 = L1->Next;
        }
        while (L2){
            LL->Next = L2;
            LL = LL->Next;
            temp2->Next = L2->Next;
            L2 = L2->Next;
        }
        return LLL;
    }
}

另外的写法：

#include<stdio.h>
#include<stdlib.h>
typedef struct node *ptrNode;
typedef ptrNode LinkList;
//头结点
typedef ptrNode Position;
//中间节点
typedef int ElementType;
struct node
{
    ElementType Element;
    Position next;
};
int IsEmpty(LinkList L)
{
    return L->next == NULL;
}
LinkList creatList(void)
{
    LinkList head, r, p;
    int x;
    head = (struct node*)malloc(sizeof(struct node));   //生成新结点
    r = head;
    scanf("%d", &x);
    while (x != -1)
    {
        p = (struct node*)malloc(sizeof(struct node));
        p->Element = x;
        r->next = p;
        r = p;
        scanf("%d", &x);
    }
    r->next = NULL;
    return head;
}
LinkList mergeList(LinkList a, LinkList b)
{
    Position ha, hb, hc;
    LinkList c, r, p;
    ha = a->next;
    hb = b->next;
    c = (struct node*)malloc(sizeof(struct node));
    r = c;
    while ((ha != NULL) && (hb != NULL))
    {
        p = (struct node*)malloc(sizeof(struct node));
        if (ha->Element <= hb->Element)
        {
            p->Element = ha->Element;
            ha = ha->next;
        }
        else{
            p->Element = hb->Element;
            hb = hb->next;
        }        
        r->next = p;
        r = p;
    }
    if (ha == NULL){
        while (hb != NULL)
        {
            p = (struct node*)malloc(sizeof(struct node));
            p->Element = hb->Element;
            hb = hb->next;
            r->next = p;
            r = p;
        }
    }
    if (hb == NULL){
        while (ha != NULL){
            p = (struct node*)malloc(sizeof(struct node));
            p->Element = ha->Element;
            ha = ha->next;
            r->next = p;
            r = p;
        }
    }
    r->next = NULL;
    return c;
}
void printList(LinkList L){
    LinkList hc;
    int flag = 0;
    hc = L->next;
    if (hc == NULL)
        printf("NULL");
    while (hc != NULL){
        if (flag)
            printf(" ");
        else
            flag = 1;
        printf("%d", hc->Element);
        hc = hc->next;
    }
}

int main(void){
    LinkList L1, L2, L3;
    L1 = creatList();
    L2 = creatList();
    L3 = mergeList(L1, L2);
    printList(L3);
    return 0;
}

reference： C++算法之 合并两个有序链表

                 PAT 两个有序链表序列的合并