6-5 链式表操作集（20 分）
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 */
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
答案：
Position Find(List L, ElementType X)
{
List pCur = L;
if (L == NULL)
{
return ERROR;
}
while (pCur != NULL)
{
if (pCur->Data == X)
{
return pCur;
}
pCur = pCur->Next;
}
return ERROR;
}
List Insert(List L, ElementType X, Position P)
{
List pCur, pPre, pM;
if (L == NULL)
{
if (P == NULL)
{
pM = (List)malloc(sizeof(struct LNode));
pM->Data = X;
pM->Next = NULL;
return pM;
}
else
{
printf("Wrong Position for Insertion\n");
return ERROR;
}
}
if (P == NULL)
{
pCur = L;
while (pCur != NULL)
{
pPre = pCur;
pCur = pCur->Next;
}
pM = (List)malloc(sizeof(struct LNode));
pM->Data = X;
pM->Next = pCur;
pPre->Next = pM;
return L;
}
pPre = pCur = L;
while (pCur != NULL)
{
if (pCur == P)
{
pM = (List)malloc(sizeof(struct LNode));
pM->Data = X;
pM->Next = pCur;
if (pPre == pCur)
{
return pM;
}
pPre->Next = pM;
return L;
}
pPre = pCur;
pCur = pCur->Next;
}
printf("Wrong Position for Insertion\n");
return ERROR;
}
List Delete(List L, Position P)
{
List pCur, pPre;
if (L == NULL)
{
printf("Wrong Position for Deletion\n");
return ERROR;
}
pPre = pCur = L;
while (pCur != NULL)
{
if (pCur == P)
{
if (pPre == pCur)
{
return pCur->Next;
}
pPre->Next = pCur->Next;
return L;
}
pPre = pCur;
pCur = pCur->Next;
}
printf("Wrong Position for Deletion\n");
return ERROR;
}