Check whether a Singly Linked List is a Palindrome

#include

#include

#include

struct node

    int num;

    struct node *next;

};

int create(struct node **);

int palin_check (struct node *, int);

void release(struct node **);

int main()

    struct node *p = NULL;

    int result, count;

    printf("Enter data into the list\n");

    count = create(&p);

    result = palin_check(p, count);

    if (result == 1)

        printf("The linked list is a palindrome.\n");

    else

        printf("The linked list is not a palindrome.\n");

    release (&p);

    return 0;

int palin_check (struct node *p, int count)

    int i = 0, j;

    struct node *front, *rear;

    while (i != count / 2)

        front = rear = p;

        for (j = 0; j < i; j++)

            front = front->next;

        for (j = 0; j < count - (i + 1); j++)

            rear = rear->next;

        if (front->num != rear->num)

            return 0;

        else

            i++;

    return 1;

int create (struct node **head)

    int c, ch, count = 0;

    struct node *temp;

do

        printf("Enter number: ");

        scanf("%d", &c);

        count++;

        temp = (struct node *)malloc(sizeof(struct node));

        temp->num = c;

        temp->next = *head;

        *head = temp;

        printf("Do you wish to continue [1/0]: ");

        scanf("%d", &ch);

    }while (ch != 0);

    printf("\n");

    return count;

 void release (struct node **head)

    struct node *temp = *head;

    while ((*head) != NULL)

        (*head) = (*head)->next;

        free(temp);

        temp = *head;

Output

Enter data into the list

Enter number: 1

Do you wish to continue [1/0]: 1

Enter number: 2

Do you wish to continue [1/0]: 1

Enter number: 3

Do you wish to continue [1/0]: 1

Enter number: 3

Do you wish to continue [1/0]: 1

Enter number: 2

Do you wish to continue [1/0]: 1

Enter number: 1

Do you wish to continue [1/0]: 0

The linked list is a palindrome.

Convert a given Singly Linked List to a Circular List

#include

#include

#include

struct node

    int num;

    struct node *next;

};

void create(struct node **);

void tocircular(struct node **);

void release(struct node **);

void display(struct node *);

int main()

    struct node *p = NULL;

    int result, count;

    printf("Enter data into the list\n");

    create(&p);

    tocircular(&p);

    printf("Circular list generated\n");

    display(p);

    release (&p);

    return 0;

 void tocircular(struct node **p)

    struct node *rear;

    rear = *p;

    while (rear->next != NULL)

        rear = rear->next;

    rear->next = *p;

 void create(struct node **head)

    int c, ch;

    struct node *temp;

do

        printf("Enter number: ");

        scanf("%d", &c);

        temp = (struct node *)malloc(sizeof(struct node));

        temp->num = c;

        temp->next = *head;

        *head = temp;

        printf("Do you wish to continue [1/0]: ");

        scanf("%d", &ch);

    while (ch != 0);

    printf("\n");

void display(struct node *head)

    struct node *temp = head;

    printf("Displaying the list elements\n");

    printf("%d\t", temp->num);

    temp = temp->next;

    while (head != temp)

        printf("%d\t", temp->num);

        temp = temp->next;

    printf("and back to %d\t%d ..\n", temp->num, temp->next->num);

void release(struct node **head)

    struct node *temp = *head;

    temp = temp->next;

    (*head)->next = NULL;

    (*head) = temp->next;

    while ((*head) != NULL)

        free(temp);

        temp = *head;

        (*head) = (*head)->next;

Output

Enter data into the list

Enter number: 1

Do you wish to continue [1/0]: 1

Enter number: 2

Do you wish to continue [1/0]: 1

Enter number: 3

Do you wish to continue [1/0]: 1

Enter number: 4

Do you wish to continue [1/0]: 1

Enter number: 5

Do you wish to continue [1/0]: 0

Circular list generated

Displaying the list elements

5          4          3          2          1          and back to 5  4 ..

Detect the Cycle in a Linked List

#include

#include

#include

struct node

    int num;

    struct node *next;

};

void create(struct node **);

void makecycle(struct node **);

void release(struct node **);

int detectcycle(struct node *);

int main()

    struct node *p = NULL;

    int result;

    printf("Enter data into the list\n");

    create(&p);

    makecycle(&p);

    printf("Identifying if a cycle exists.\n");

    result = detectcycle(p);

    if (result)

        printf("Cycle detected in the linked list.\n");

    else

        printf("No cycle detected in the linked list.\n");

    release (&p);

    return 0;

 void makecycle(struct node **p)

    struct node *rear, *front;

    int n, count = 0, i;

    front = rear = *p;

    while (rear->next != NULL)

        rear = rear->next;

        count++;

    if (count)

        n = rand() % count;

    else

        n = 1;

    for (i = 0; i < n - 1; i++)

        front = front->next;

    rear->next = front;

int detectcycle(struct node *head)

    int flag = 1, count = 1, i;

    struct node *p, *q;

    p = q = head;

    q = q->next;

    while (1)

        q = q->next;

        if (flag)

            p = p->next;

        if (q == p)

            q = q->next;

            while (q != p)

                count++;

                q = q->next;

            q = p = head;

            for (i = 0; i < count; i++)

                q = q->next;

            while (p != q)

                p = p->next;

                q = q->next;

            q->next = NULL;

        return 1;

        else if (q->next == NULL)

            return 0;

        flag = !flag;

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 release(struct node **head)

    struct node *temp = *head;

    temp = temp->next;

    while ((*head) != NULL)

        free(temp);

        temp = *head;

        (*head) = (*head)->next;

Output

Enter data into the list

Enter number: 1

Do you wish to continue [1/0]: 1

Enter number: 2

Do you wish to continue [1/0]: 1

Enter number: 3

Do you wish to continue [1/0]: 1

Enter number: 4

Do you wish to continue [1/0]: 1

Enter number: 5

Do you wish to continue [1/0]: 1

Enter number: 6

Do you wish to continue [1/0]: 1

Enter number: 7

Do you wish to continue [1/0]: 0

Identifying if a cycle exists.

Cycle detected in the linked list..