【PTA】6-6 带头结点的链式表操作集 (20分)

【PTA】6-6 带头结点的链式表操作集 (20分)

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 

函数实现细节：

List MakeEmpty(){
    List L=(List)malloc(sizeof(struct LNode));
    L->Data=0;
    L->Next=NULL;
    return L;
}
Position Find( List L, ElementType X ){
    if (L->Next==NULL)return NULL;
    L=L->Next;
    while(L&&L->Data!=X){
        L=L->Next;
    }
    if(L==NULL){
        return NULL;
    }else if(L->Data==X){
        return L;
    }
}
 
bool Insert( List L, ElementType X, Position P ){
    Position temp=(Position)malloc(sizeof(struct LNode));
    if(L->Next==P){
        temp->Data=X;temp->Next=P;
        L->Next=temp;
        return true;
    }
    List Q=L->Next;
    while(Q->Next!=NULL&&Q->Next!=P)Q=Q->Next;
    if(P==NULL){
        temp->Data=X;temp->Next=NULL;
        Q->Next=temp;
        return true; 
        
    }else if(P &&Q->Next==NULL){
        printf("Wrong Position for Insertion
");
        return false;
    }
     temp->Data=X;temp->Next=P;
     Q->Next=temp;
     return true;
}
 
bool Delete( List L, Position P ){
    if (L->Next==NULL)return false;
    List Q=L->Next;
    if(P==Q){
        L->Next=P->Next;
        free(P);
        return true;
    }
    while(Q->Next!=P&&Q->Next!=NULL)
    {
        Q=Q->Next;
    }
    if(Q->Next==NULL){
           printf("Wrong Position for Deletion
");
           return false;
     }else{
         Q->Next=P->Next;
           free(P);
         return true;
      }
}