linkedlist.cpp

#include<stdio.h>
#include<stdlib.h>


#define NULL_VALUE -99999
#define SUCCESS_VALUE 99999

struct listNode
{
    int item;
    struct listNode * next;
};

struct listNode * list;

void initializeList()
{
    list = 0;  //initially set to NULL
}

int insertItem(int item) //insert at the beginning of the linked list
{
    struct listNode * newNode ;
    newNode = (struct listNode*) malloc (sizeof(struct listNode)) ;
    newNode->item = item ;
    newNode->next = list ; //point to previous first node
    list = newNode ; //set list to point to newnode as this is now the first node
    return SUCCESS_VALUE ;
}


int deleteItem(int item)
{
    struct listNode *temp, *prev ;
    temp = list ; //start at the beginning
    while (temp != 0)
    {
        if (temp->item == item) break ;
        prev = temp;
        temp = temp->next ; //move to next node
    }
    if (temp == 0) return NULL_VALUE ; //item not found to delete
    if (temp == list) //delete the first node
    {
        list = list->next ;
        free(temp) ;
    }
    else
    {
        prev->next = temp->next ;
        free(temp);
    }
    return SUCCESS_VALUE ;
}


struct listNode * searchItem(int item)
{
    struct listNode * temp ;
    temp = list ; //start at the beginning
    while (temp != 0)
    {
        if (temp->item == item) return temp ;
        temp = temp->next ; //move to next node
    }
    return 0 ; //0 means invalid pointer in C, also called NULL value in C
}

void printList()
{
    if(list==0){
        printf("NO ELEMENT\n");
        return;
    }
    struct listNode * temp;
    temp = list;
    while(temp!=0)
    {
        printf("%d->", temp->item);
        temp = temp->next;
    }
    printf("\n");
}

int insertLast(int item)
{

    struct listNode *current_node=list;
    while(current_node->next!=0)
    {

        current_node=current_node->next;

    }
    struct listNode * temp ;
    temp = (struct listNode*) malloc (sizeof(struct listNode)) ;
    temp->item=item;
    temp->next=0;
    current_node->next=temp;
    return SUCCESS_VALUE;

}

int insertBefore(int oldItem, int newItem)
{
    struct listNode *temp, *prev ;
    temp = list ; //start at the beginning
    while (temp != 0)
    {
        if (temp->item == oldItem) break ;
        prev = temp;
        temp = temp->next ; //move to next node
    }
    if (temp == 0)
    {
        insertItem(newItem) ;
        return SUCCESS_VALUE;
    } //item not found to delete
    if (temp == list)
    {
        insertItem(newItem) ;

        return SUCCESS_VALUE;

    }
    else
    {


        struct listNode * newNode ;
        newNode = (struct listNode*) malloc (sizeof(struct listNode)) ;
        newNode->item=newItem;
        newNode->next=temp;
        prev->next=newNode;
        return SUCCESS_VALUE;
    }
    return SUCCESS_VALUE ;
}

int deleteAfter(int item)
{
    struct listNode *newNode=searchItem(item);
    if(newNode==0||newNode->next==0){

        return NULL_VALUE;
    }

    else {
           struct listNode *temp=newNode->next;
           newNode->next=temp->next;
           free(temp);

    }

}

int deleteLast()
{
    if(list==0) return NULL_VALUE;
    struct listNode *temp, *prev ;
    temp = list ; //start at the beginning
    while (temp->next != 0)
    {

        prev = temp;
        temp = temp->next ; //move to next node
    }
    if (temp == 0) return NULL_VALUE ; //item not found to delete
    if (temp == list) //delete the first node
    {
        list = 0;
        free(temp) ;
    }
    else
    {
        prev->next = 0 ;
        free(temp);
    }
    return SUCCESS_VALUE ;


}



int main(void)
{
    initializeList();
    while(1)
    {
        printf("1. Insert new item. \n2. Delete item. \n3. Search item. \n");
        printf("4. Insert at Last . \n5.Insert before an old Value \n6.DeleteAfter \n7.Delete Last \n8. Print. \n9. exit.\n");

        int ch;
        scanf("%d",&ch);
        if(ch==1)
        {
            int item;
            scanf("%d", &item);
            insertItem(item);
        }
        else if(ch==2)
        {
            int item;
            scanf("%d", &item);
            deleteItem(item);
        }
        else if(ch==3)
        {
            int item;
            scanf("%d", &item);
            struct listNode * res = searchItem(item);
            if(res!=0) printf("Found.\n");
            else printf("Not found.\n");
        }
        else if(ch==4)
        {
            int item;
            scanf("%d",&item);
            insertLast(item);
        }
        else if(ch==5)
        {
            int old,New;
            printf("Insert oldItem:");
            scanf("%d",&old);
            printf("Insert newItem:");
            scanf("%d",&New);
            insertBefore(old,New );

        }else if(ch==6){
        int item;
        scanf("%d",&item);
        deleteAfter(item);
        }
        else if(ch==7){
            deleteLast();
        }
        else if(ch==8)
        {
            printList();
        }
        else if(ch==9)
        {
            break;
        }
    }

}