6-5 linked list operation set (20 points)

This problem requires to realize the operation set of linked list.

Function interface definition:

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

The List structure is defined as follows:

typedef struct LNode *PtrToLNode;
struct LNode {
    ElementType Data;
    PtrToLNode Next;
};
typedef PtrToLNode Position;
typedef PtrToLNode List;

Each operation function is defined as:

Position find (List L, ElementType x): returns the first occurrence of X in a linear table. If not found, ERROR will be returned;

List insert (List L, ElementType X, position P): insert X before the node pointed to by position P, and return the header of the linked list. If the parameter p points to an illegal position, print "Wrong Position for Insertion" and return ERROR;

List delete (List L, position P): delete the element of position P and return the header of the linked list. If parameter p points to an illegal location, print "Wrong Position for Deletion" and return ERROR.

Sample referee test procedure:

#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;
}

/* Your code will be embedded here */

Input example:

6
12 2 4 87 10 2
4
2 12 87 5

Output example:

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

ANS: 

Position Find( List L, ElementType X )
{
    List l=L;
    for(; l!=NULL; l=l->Next)
    {
        if(l->Data==X)
            return l;
    }
    return ERROR;
}
List Insert( List L, ElementType X, Position P )
{

    if(L==NULL)
    {
        L=(List) malloc(sizeof(struct LNode));
        L->Data=X;
        L->Next=NULL;
        return L;
    }
   /* if(P==NULL)
     {
         printf("Wrong Position for Insertion");
         return ERROR;
     }*/
    List t=(List) malloc(sizeof(struct LNode)),y=L;
    t->Data=X;
    if(L==P)
    {
        t->Next=L;
        return t;
    }
    while(y->Next!=P)
    {
        y=y->Next;
        if(y==NULL)
        {
            printf("Wrong Position for Insertion\n");
            return ERROR;
        }
    }
    y->Next=t;
    t->Next=P;
    return L;
}
List Delete( List L, Position P )
{

    List t=L;
    if(t==P)
    {
        L=L->Next;
        return L;
    }
    while(t->Next!=P)
    {
        t=t->Next;
        if(t==NULL)
        {
            printf("Wrong Position for Deletion\n");
            return ERROR;
        }
    }
    t->Next=P->Next;
    free(P);
    return L;
}