Wednesday, October 29, 2014

C Pointer Program

Implement Doubly Linked List using Singly Linked List

#include 
#include 
struct node
{
    int num;
    struct node *next;
};
void create(struct node **);
void move (struct node *);
void release(struct node **);
void display(struct node *);
int main()
{
    struct node *p = NULL, *q = NULL;
    int result, count;
    printf("Enter data into the list\n");
    create(&p);
    printf("Displaying list:\n");
    display(p);
    move(p);
    release (&p);
    return 0;
}
void move(struct node *head)
{
    struct node *p, *q;
    int ch;
    p = q = head;
    printf("\nPointer at %d\n", head->num);
    do
    {
        printf("Select option:\n1. Move front\n2. Move back\n3. Exit\nYour choice: ");
        scanf("%d", &ch);
        switch(ch)
        {
        case 1: if(q->next != NULL)
                {
                    q = q->next;
                    printf("\nPointer at %d\n", q->num);
                }
                else
                {
                    printf("\nPointer at last node %d. Cannot move ahead.\n", q->num);
                }
                break;
        case 2: while (p->next != q)
                {
                    p = p->next;
                }
                if (p == q)
                {
                    printf("\nPointer at first node %d. Cannot move behind.\n", q->num);
                }
                else
                {
                    q = p;
                    p = head;
                    printf("\nPointer at %d\n", q->num);
                }
                break;
        case 3: return;
        default: printf("\nInvalid choice entered. Try again\n");
        }
    } while (1);
}
 
void create(struct node **head)
{
    int c, ch;
    struct node *temp, *rear;
 
    do
    {
        printf("Enter number: ");
        scanf("%d", &c);
        temp = (struct node *)malloc(sizeof(struct node));
        temp->num = c;
        temp->next = NULL;
        if (*head == NULL)
        {
            *head = temp;
        }
        else
        {
            rear->next = temp;
        }
        rear = temp;
        printf("Do you wish to continue [1/0]: ");
        scanf("%d", &ch);
    } while (ch != 0);
    printf("\n");
}
 
void display(struct node *head)
{
    while (head != NULL)
    {
        printf("%d\t", head->num);
        head = head->next;
    }
    printf("\n");
}
 
void release(struct node **head)
{
    struct node *temp;
    while ((*head) != NULL)
    {
        temp = *head;
        (*head) = (*head)->next;
        free(temp);
    }
}
 
Output
 
Enter data into the list
Enter number: 2
Do you wish to continue [1/0]: 1
Enter number: 4
Do you wish to continue [1/0]: 1
Enter number: 6
Do you wish to continue [1/0]: 1
Enter number: 8
Do you wish to continue [1/0]: 1 
Enter number: 10
Do you wish to continue [1/0]: 0
 
Displaying list:
2          4          6          8          10        
 
Pointer at 2
Select option:
1. Move front
2. Move back
3. Exit
Your choice: 1
 
Pointer at 4
Select option:
1. Move front
2. Move back
3. Exit

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