4-5 链式表操作集 (20分) PTA

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“WrongPosition 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“WrongPosition for Deletion”并返回ERROR。

裁判测试程序样例：

#include <stdio.h>#include <stdlib.h>#define ERROR NULLtypedef 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");elseprintf("%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

思路：略

原题传送门：https://pta.patest.cn/pta/test/15/exam/3/question/728

Position Find( List L, ElementType X ){List P = L;while(P){if(P->Data == X) return P;P = P->Next;}return ERROR; }  List Insert( List L, ElementType X, Position P ) { 	List head=L; 	List P1;    if(L==P){head=(List)malloc(sizeof(struct LNode));    head->Data=X;head->Next=P;return head;    }    while(L){        if(L->Next==P) break;        L=L->Next;    }    if(!L){printf("Wrong Position for Insertion\n");    	return ERROR;    }    P1=(List)malloc(sizeof(struct LNode));    P1->Data=X;    P1->Next=P;L->Next = P1;return head; } List Delete( List L, Position P ) { 	if(L==P){L=L->Next;    	return L;}    List head=L;while(L){    if(L->Next==P)break;    L=L->Next;}if(!L){printf("Wrong Position for Deletion\n");    	return ERROR;}L->Next=P->Next;free(P);    	return head; }