doublyLinkedList.c

#define NULL_VALUE -99999
#define SUCCESS_VALUE 99999
struct listNode
{
    int item ; //will be used to store value
    struct node *next ; //will keep address of next node
    struct node *prev ; //will keep address of previous node
} ;
struct listNode * list ;
struct listNode * tail ;

void initializeList()
{
    printf("\n--------->Initializing<---------\n");
    list = 0 ; //set to NULL
    tail = 0 ; //set to NULL
}


int insertAtFirst(int data)
{

    struct listNode *newNode, *head;
    newNode = (struct listNode*)malloc(sizeof(struct listNode));
    newNode->item = data;       //Insert data on new item
    newNode->next = list;       //point next node by list value;
    newNode->prev = 0;          //no previous node at first;
    list = newNode;

    head = newNode->next;
    if(head != 0){

        head->prev = newNode;
    }

    else
        tail = newNode; //first inserted node act as tail;
    return SUCCESS_VALUE ;

}


int insertAtLast(int data)
{

    struct listNode *newNode, *head;
    newNode = (struct listNode*)malloc(sizeof(struct listNode));
    newNode->item = data;       //Insert data on new item
    newNode->prev = tail;       //point prev node as tail
    newNode->next = 0;          //no previous node at last;
    tail = newNode;

    head = newNode->prev;
    if(head != 0){
        head->next = newNode;
    }

    else
        list = newNode; //first inserted node act as listHead;
    return SUCCESS_VALUE ;

}


// Delete or remove the first node

void deleteFromFirst()
{
    struct node * toDelete;

    if(list == 0)
    {
        printf("Unable to delete. List is empty.\n");
    }
    else
    {
        toDelete = list;

        list = list->next; // Move head pointer to 2 node

        if (list != 0)
            list->prev = 0; // Remove the link to previous node

        free(toDelete); // Delete the first node from memory
        printf("\nDeleted\n");
    }
}

// Delete or remove the last node
void deleteFromLast()
{
    struct node * toDelete;

    if(tail == 0)
    {
        printf("Unable to delete. List is empty.\n");
    }
    else
    {
        toDelete = tail;

        tail = tail->prev; // Move head pointer to 2 node

        if (tail != 0)
            tail->next = 0; // Remove the link to previous node

        free(toDelete); // Delete the first node from memory
        printf("\nDeleted\n");
    }
}

//Delete from position;
void deleteFromPos(int position)
{
    struct listNode *current, *tempNode;
    int i;

    current = list;
    for(i=1; i<position && current!=0; i++)
    {
        current = current->next;
    }

    if(position == 1)
        deleteFromFirst();
    else if(position < 1)
        printf("Invalid position!\n");

    else if(current == tail)
        deleteFromLast();
    else if(current != 0)
    {
        tempNode = current->prev;
        tempNode->next = current->next;
        tempNode = current->next;
        tempNode->prev = current->prev;

        free(current); // Delete the n node

         printf("\nDeleted\n");
    }
    else
        printf("Invalid position!\n");
}


// Show all node values
void showDoublyList()
{
    struct listNode * tmp, *tempNode;
    int n = 1;
    if(list == 0)
    {
        printf(" No data found in the List.");
    }
    else
    {
        tmp = list;
        printf("\n\n List Data are :\n");

        while(tmp != 0)
        {
            printf(" node %d : %d\t", n, tmp->item);


            tempNode = tmp->prev;
            if(tempNode != 0)
                printf("(prev: %d)",tempNode->item);
            else
                printf("(prev: 0)");

            tempNode = tmp->next;

            if(tempNode != 0)
                printf("(next: %d)",tempNode->item);
            else
                printf("(next: 0)");


            printf("\n");
            n++;
            tmp = tempNode;
        }
    }
}

// Show all node values reverst
void showDoublyListReverse()
{
    struct listNode * tmp, *tempNode;
    printf("\n\nReverse Print");
    int n = 1;
    if(tail == 0)
    {
        printf(" No data found in the List.");
    }
    else
    {
        tmp = tail;
        printf("\n\n List Data are :\n");

        while(tmp != 0)
        {
            printf(" node %d : %d\t", n, tmp->item);

            tempNode = tmp->next;

            if(tempNode != 0)
                printf("(next: %d)",tempNode->item);
            else
                printf("(next: 0)");

            tempNode = tmp->prev;
            if(tempNode != 0)
                printf("(prev: %d)",tempNode->item);
            else
                printf("(prev: 0)");


            printf("\n");
            n++;
            tmp = tempNode;
        }
    }
}

int main()
{
    initializeList();
    showDoublyList();
    insertAtLast(2);
    insertAtLast(4);
    insertAtLast(5);
    insertAtLast(6);
    showDoublyList();

    initializeList();
    insertAtFirst(1);
    insertAtFirst(41);
    insertAtFirst(12);
    insertAtFirst(6);
    showDoublyList();

    //deleteFromFirst();
    //showDoublyList();

    //deleteFromLast();
    //showDoublyList();


    deleteFromPos(0);
    showDoublyList();


    return 0;
}