数据结构及算法——带头结点的链式表操作集（C语言）

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 NULLtypedef 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");    else        printf("%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

【答案】：

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