tower_of_hannoi.c

/* Code to solve the problem of tower of hannoi.
Algorithm:
1. This code shifts n-1 elements to an auxillary array
2. Then shift the nth element to final array
3. Then swaps the initial and the auxillary array and repeat the procedure.

* Here for ease of list starting location handling(as it change frequently)
  I have used an extra element at the starting of each list pointing to the main
  starting of the lists.*/

#include<stdio.h>
#include<stdlib.h>
struct link_list
{
int num;
struct link_list *next;
};
       typedef struct link_list Node;

       void push(Node *first,int num)
       {
             Node* temp=(Node*)malloc(sizeof(Node));
             temp->num=num;
             temp->next=first->next;
             first->next=temp;
             }

       int pop(Node *first)
       {
             Node* prev=first->next;
             first->next=(first->next)->next;
             int pop=prev->num;
             free(prev);
             return pop;
             }

       void display(Node *first)
       {
            Node* list=first->next;
            while(list!=0)
            {
            printf("%d \n",list->num);
            list=list->next;
            }
            getch();
       }

       void toh(Node *a,Node *b, Node *c, int n)
       {
            if(n==1)
            {
            int p=pop(a);
            push(b,p);
            }
            else
            {
             toh(a,c,b,n-1);

             int p=pop(a);
             push(b,p);

             toh(c,b,a,n-1);
            }
       }

       main()
       {
          Node *a,*b,*c;
          a=(Node*)malloc(sizeof(Node));
          b=(Node*)malloc(sizeof(Node));
          c=(Node*)malloc(sizeof(Node));
          a->next=b->next=c->next=0;

          int i,j;
          printf("Enter the number of digits of which tower of hannoi is to be solved. -->  ");
          scanf("%d",&j);
          for(i=j;i>=1;i--)
          push(a,i);

          toh(a,b,c,j);
          display(b);
       }