PTA数据结构与算法题目集（中文） 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");elseprintf("%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 

实现代码：

List MakeEmpty(){List L;L=(List)malloc(sizeof(struct LNode));L->Next=NULL;return L; 
} 
Position Find( List L, ElementType X ){List p=L->Next;while(p){if(p->Data==X)return p;p=p->Next; }return ERROR;
}
bool Insert( List L, ElementType X, Position P ){List t=L,q;if(t->Next==NULL){q=(List)malloc(sizeof(struct LNode));q->Data=X;q->Next=NULL;L->Next=q;return true;}while(t){if(t->Next==P){q=(List)malloc(sizeof(struct LNode));q->Data=X;q->Next=t->Next;t->Next=q;return true;}t=t->Next;}printf("Wrong Position for Insertion\n");return false;
}
bool Delete( List L, Position P ){List t=L;if(P==ERROR||t->Next==NULL){printf("Wrong Position for Deletion\n");return false;}		while(t){if(t->Next==P){t->Next=t->Next->Next;return true;}t=t->Next;}printf("Wrong Position for Deletion\n");return false;
}
void printList(List L){List p=L->Next;while(p){printf("%d ",p->Data);p=p->Next;}printf("\n");
}