6-6 带头结点的链式表操作集

https://pintia.cn/problem-sets/15/problems/729

本题要求实现带头结点的链式表操作集。

函数接口定义：

List MakeEmpty(); 
Position Find( List L, ElementType X );
bool Insert( List L, ElementType X, Position P );
bool Delete( List L, Position P );

其中List结构定义如下：

typedef struct LNode *PtrToLNode;
struct LNode {
    ElementType Data;
    PtrToLNode Next;
};
typedef PtrToLNode Position;
typedef PtrToLNode List;

各个操作函数的定义为：

List MakeEmpty()：创建并返回一个空的线性表；

Position Find( List L, ElementType X )：返回线性表中X的位置。若找不到则返回ERROR；

bool Insert( List L, ElementType X, Position P )：将X插入在位置P指向的结点之前，返回true。如果参数P指向非法位置，则打印“Wrong Position for Insertion”，返回false；

bool Delete( List L, Position P )：将位置P的元素删除并返回true。若参数P指向非法位置，则打印“Wrong Position for Deletion”并返回false。

裁判测试程序样例：

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

#define ERROR NULL
typedef enum {false, true} bool;
typedef int ElementType;
typedef struct LNode *PtrToLNode;
struct LNode {
    ElementType Data;
    PtrToLNode Next;
};
typedef PtrToLNode Position;
typedef PtrToLNode List;

List MakeEmpty(); 
Position Find( List L, ElementType X );
bool Insert( List L, ElementType X, Position P );
bool Delete( List L, Position P );

int main()
{
    List L;
    ElementType X;
    Position P;
    int N;
    bool flag;

    L = MakeEmpty();
    scanf("%d", &N);
    while ( N-- ) {
        scanf("%d", &X);
        flag = Insert(L, X, L->Next);
        if ( flag==false ) printf("Wrong Answer
");
    }
    scanf("%d", &N);
    while ( N-- ) {
        scanf("%d", &X);
        P = Find(L, X);
        if ( P == ERROR )
            printf("Finding Error: %d is not in.
", X);
        else {
            flag = Delete(L, P);
            printf("%d is found and deleted.
", X);
            if ( flag==false )
                printf("Wrong Answer.
");
        }
    }
    flag = Insert(L, X, NULL);
    if ( flag==false ) printf("Wrong Answer
");
    else
        printf("%d is inserted as the last element.
", X);
    P = (Position)malloc(sizeof(struct LNode));
    flag = Insert(L, X, P);
    if ( flag==true ) printf("Wrong Answer
");
    flag = Delete(L, P);
    if ( flag==true ) printf("Wrong Answer
");
    for ( P=L->Next; P; P = P->Next ) printf("%d ", P->Data);
    return 0;
}
/* 你的代码将被嵌在这里 */

输入样例：

6
12 2 4 87 10 2
4
2 12 87 5

输出样例：

2 is found and deleted.
12 is found and deleted.
87 is found and deleted.
Finding Error: 5 is not in.
5 is inserted as the last element.
Wrong Position for Insertion
Wrong Position for Deletion
10 4 2 5 

提交代码（not mine）

List MakeEmpty()
{
    List tmp = (List)malloc(sizeof(struct LNode));
    tmp->Next=NULL;
    return tmp;
}

Position Find( List L, ElementType X )
{
    while(L&&L->Next)
    {
        if(L->Data == X)
            return L;
        L = L->Next;
    }
    if(L->Data==X)
        return L;
    return ERROR;
}
bool Insert( List L, ElementType X, Position P )
{
    List p=(List)malloc(sizeof(struct LNode));
    p->Data=X;
    p->Next=NULL;
    List pb=L;
    if(L==P)
    {
        p->Next=L;
        L=p;
        return true;
    }
    while(pb->Next!=P&&pb->Next!=NULL)
    {
        pb=pb->Next;
    }
    if(pb->Next==P)
    {
        p->Next=P;
        pb->Next=p;
        return true;
    }
    else
        printf("Wrong Position for Insertion
");
    return false;
}
bool Delete( List L, Position P )
{
    List pb=L;
    if(L==NULL)
    {
        printf("Wrong Position for Deletion
");
        return false;
    }
    if(L==P)
    {
        L=L->Next;
        return true;
    }
    while(pb->Next!=P&&pb->Next!=NULL)
    {
        pb=pb->Next;
    }
    if(pb->Next==P)
    {
        pb->Next=P->Next;
        return true;
    }
    else
        printf("Wrong Position for Deletion
");
    return false;
}