Solve Tower of Hanoi Problem using Recursion

#include

#include

void towers(int, char, char, char);

int main()

    int num;

    clrscr();

    printf("Enter the number of disks : ");

    scanf("%d", &num);

    printf("The sequence of moves involved in the Tower of Hanoi are :\n");

    towers(num, 'A', 'C', 'B');

    return 0;

void towers(int num, char frompeg, char topeg, char auxpeg)

    if (num == 1)

        printf("\n Move disk 1 from peg %c to peg %c", frompeg, topeg);

        return;

    towers(num - 1, frompeg, auxpeg, topeg);

    printf("\n Move disk %d from peg %c to peg %c", num, frompeg, topeg);

    towers(num - 1, auxpeg, topeg, frompeg);

    getch();

Output

Enter the number of disks : 3

The sequence of moves involved in the Tower of Hanoi are :

Move disk 1 from peg A to peg C

Move disk 2 from peg A to peg B

Move disk 1 from peg C to peg B

Move disk 3 from peg A to peg C

Move disk 1 from peg B to peg A

Move disk 2 from peg B to peg C

Move disk 1 from peg A to peg C

Reverse only First N Elements of a Linked List

#include

#include

#include

struct node

    int num;

    struct node *next;

};

void create(struct node **);

void reverse(struct node **, int);

void release(struct node **);

void display(struct node *);

int main()

    struct node *p = NULL;

    int n;

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

    create(&p);

    printf("Displaying the nodes in the list:\n");

    display(p);

    printf("Enter the number N to reverse first N node: ");

    scanf("%d", &n);

    printf("Reversing the list...\n");

    if (n > 1)

        reverse(&p, n - 2);

    printf("Displaying the reversed list:\n");

    display(p);

    release(&p);

    return 0;

void reverse(struct node **head, int n)

    struct node *p, *q, *r, *rear;

    p = q = r = *head;

    if (n == 0)

        q = q->next;

        p->next = q->next;

        q->next = p;

        *head = q;

    else

        p = p->next->next;

        q = q->next;

        r->next = NULL;

        rear = r;

        q->next = r;

        while (n > 0 && p != NULL)

            r = q;

            q = p;

            p = p->next;

            q->next = r;

            n--;

        *head = q;

        rear->next = p;

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 *p)

    while (p != NULL)

        printf("%d\t", p->num);

        p = p->next;

    printf("\n");

 void release(struct node **head)

    struct node *temp = *head;

    *head = (*head)->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

Displaying the nodes in the list:

1   2          3          4          5          6          7

Enter the number N to reverse first N node: 4

Reversing the list...

Displaying the reversed list:

4   3          2          1          5          6          7