6-5 链式表操作集

本题要求实现链式表的操作集。

函数接口定义：

Position Find( List L, ElementType X );
List Insert( List L, ElementType X, Position P );
List 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：

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

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

List Delete( List L, Position P )：将位置P的元素删除并返回链表的表头。若参数P指向非法位置，则打印“Wrong Position for Deletion”并返回ERROR。

裁判测试程序样例：

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

#define ERROR NULL
typedef int ElementType;
typedef struct LNode *PtrToLNode;
struct LNode {
    ElementType Data;
    PtrToLNode Next;
};
typedef PtrToLNode Position;
typedef PtrToLNode List;

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

int main()
{
    List L;
    ElementType X;
    Position P, tmp;
    int N;

    L = NULL;
    scanf("%d", &N);
    while ( N-- ) {
        scanf("%d", &X);
        L = Insert(L, X, L);
        if ( L==ERROR ) 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 {
            L = Delete(L, P);
            printf("%d is found and deleted.\n", X);
            if ( L==ERROR )
                printf("Wrong Answer or Empty List.\n");
        }
    }
    L = Insert(L, X, NULL);
    if ( L==ERROR ) printf("Wrong Answer\n");
    else
        printf("%d is inserted as the last element.\n", X);
    P = (Position)malloc(sizeof(struct LNode));
    tmp = Insert(L, X, P);
    if ( tmp!=ERROR ) printf("Wrong Answer\n");
    tmp = Delete(L, P);
    if ( tmp!=ERROR ) printf("Wrong Answer\n");
    for ( P=L; P; P = P->Next ) printf("%d ", P->Data);
    return 0;
}

/* 你的代码将被嵌在这里 */

Position newNode(ElementType X);

Position Find(List L, ElementType X) {
    List q = L;
    if (q == NULL)
        return ERROR;
    while (q != NULL) {
        if (q->Data == X)
            return q;
        else
            q = q->Next;
    }
    return ERROR;
}

List Insert(List L, ElementType X, Position P) {

    Position pTemp = L;
    Position pNew = newNode(X);
    if (L != NULL) {
        if (P == L) { //在表头插入（表头不是其余节点的后继，比较特殊）
            pNew->Next = pTemp;
            L = pNew;
        }
        else { //在表中插入
            while (pTemp->Next != P) {
                pTemp = pTemp->Next;
                if (pTemp == NULL) { //说明L中没有P所指向的位置
                    printf("Wrong Position for Insertion\n");
                    return ERROR;
                }
            }
            pNew->Next = P;
            pTemp->Next = pNew;
        }
    }
    else //L==NULL && P==NULL的情况
        L = pNew;
    return L;
}

List Delete(List L, Position P) {
    if (P == NULL || L == NULL) {
        printf("Wrong Position for Deletion\n");
        return ERROR;
    }
    Position pTemp = L;
    if (P == L) {//在表头删除（表头不是其余节点的后继，比较特殊）
        L = L->Next;
    }
    else { //在表中删除
        while (pTemp->Next != P) {
            pTemp = pTemp->Next;
            if (pTemp == NULL) { //说明L中没有P所指向的位置
                printf("Wrong Position for Deletion\n");
                return ERROR;
            }
        }
        pTemp->Next = P->Next;
    }
    free(P);
    return L;
}

Position newNode(ElementType X) {
    Position pNew = (Position)malloc(sizeof(struct LNode));
    if (pNew == NULL)
        exit(-1);
    else {
        pNew->Data = X;
        pNew->Next = NULL;
        return pNew;
    }
}