6-6 带头结点的链式表操作集

6-6 带头结点的链式表操作集（20 分）

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\n");
    }
    scanf("%d", &N);
    while ( N-- ) {
        scanf("%d", &X);
        P = Find(L, X);
        if ( P == ERROR )
            printf("Finding Error: %d is not in.\n", X);
        else {
            flag = Delete(L, P);
            printf("%d is found and deleted.\n", X);
            if ( flag==false )
                printf("Wrong Answer.\n");
        }
    }
    flag = Insert(L, X, NULL);
    if ( flag==false ) printf("Wrong Answer\n");
    else
        printf("%d is inserted as the last element.\n", X);
    P = (Position)malloc(sizeof(struct LNode));
    flag = Insert(L, X, P);
    if ( flag==true ) printf("Wrong Answer\n");
    flag = Delete(L, P);
    if ( flag==true ) printf("Wrong Answer\n");
    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

思路：大家好，我叫签到题😋

List MakeEmpty()
{
    List list = (List)malloc(sizeof(struct LNode));
    list->Data = 0;
    list->Next = NULL;

    return list;
}
Position Find(List L, ElementType X)
{
    List list = L->Next;
    int flag = 0;
    for (int i = 0; i < L->Data; i++){
        if (list->Data == X) {
            flag = 1; break;
        }
        else list = list->Next;
    }
    
    return flag == 1 ? list : ERROR;

}
bool Insert(List L, ElementType X, Position P)
{
    List list = L;
    int flag = 0;
    List temp = (List)malloc(sizeof(struct LNode));
    temp->Data = X;
    temp->Next = NULL;

    for (int i = 0; i <= L->Data; i++, list = list->Next)
        if (list->Next == P)
        {
            flag = 1; break;
        }

        if (flag){
            temp->Next = list->Next;
            list->Next = temp;
            L->Data++;
            return true;
        }
        printf("Wrong Position for Insertion\n");
        return false;
    

}
bool Delete(List L, Position P)
{
    List list = L;
    int flag = 0;
    for (int i = 0; i < L->Data; i++, list = list->Next)
    if (list->Next == P)
    {
        flag = 1; break;
    }

    if (flag){ list->Next = list->Next->Next; L->Data--; return true; }
    printf("Wrong Position for Deletion\n");
    return false;
}