Find loop in a single linked list & remove it

/* How would you detect a loop in a linked list & remove it? */

/*Ref: http://vijayinterviewquestions.blogspot.in/2007/05/how-would-you-detect-loop-in-linked.html*/

/* http://www.geeksforgeeks.org/archives/12225 */

#include <stdio.h>

#include <malloc.h>

typedef struct singlelink node;

struct singlelink

{

                int data;

                node *next;

};

void append(node **q,int num);

void display(node *temp);

void append(node **q,int num)

{

    node *temp=*q,*r;

                r = (node *)malloc(sizeof(node));

                r->data = num;

                r->next = NULL;

                if(temp==NULL) *q=r;

                else

                {

                                while(temp->next!=NULL)

                                                temp = temp->next;

                                temp->next = r;

                }

}

void display(node *temp)

{

                printf("\nThe list:\n");

                while(temp)

                {

                                printf("%d ",temp->data);

                                temp=temp->next;

                }

}

void createloop(node *q);

void createloop(node *q)

{

                node *temp=q;

                node *node2=NULL;

                node2=temp->next;

                while(temp->next !=NULL)

                {              temp=temp->next;}

                temp->next=node2;

}

#define DEBUG2              1

void removeloop(node *p, node *tmp);

void removeloop(node *p, node *tmp)

{

                node *temp1=p;

                node *temp2=p;

                unsigned int cnt=1,i;

                /* Count the no. of nodes in the loop */

                while(temp1->next != temp2)

                {

                                temp1 = temp1->next;

                                cnt++;

                }

                /* Fix one pointer to head & the other to cnt^th node from head */

                temp1=temp2=tmp;

                for(i=0;i

                                temp2=temp2->next;

                /* Move both pointers at the same pace, they will meet at the loop starting node */

                while(temp1 != temp2)

                {

                                temp1=temp1->next;

                                temp2=temp2->next;

                }

                /* Get pointer to the last node of loop & make next of it as NULL */

                temp2=temp2->next;

                while(temp2->next != temp1)

                                temp2 = temp2->next;

                temp2->next=NULL;

}

/* Floyd cycle detection algorithm */

void findloop(node *tmp);

void findloop(node *tmp)

{

                /* Have 2 pointers to start of the linked list.

                   Increment one pointer by 1 node and the other by 2 nodes.

                   If there's a loop, the 2nd pointer will meet the 1st pointer somewhere.

                   If it does, then you know there's one.

                */

                node *p,*q;

                p=q=tmp;

                while(p && q && q->next)

                {

                                p=p->next;

                                q=q->next->next;

                                if(p==q)

                                {

                                                printf("Loop detected..\n");

                                                removeloop(p,tmp);

                                                return;

                                }

                }

}

int main(void)

{

                node *head=NULL;

                int i;

                for(i=0;i<10;i++)

                                append(&head,i);

                display(head);

                createloop(head);

                printf("\nOK...\n");

                findloop(head);

                display(head);

                return 0;

}

/*

void findloop(node *tmp)

{

                // Have 2 pointers to start of the linked list.

                //   Increment one pointer by 1 node and the other by 2 nodes.

                //   If there's a loop, the 2nd pointer will meet the 1st pointer somewhere.

                //   If it does, then you know there's one.

                node *p,*q;

                p=tmp;

                q=p->next;

                while(p!=NULL && q!=NULL)

                {

                                if(p==q)

                                {

                                                printf("Loop detected..\n");

                                                removeloop(p,tmp);

                                                return;

                                }

                                p=p->next;

                                q=(q->next)?(q->next->next):(q->next);

                }

}

*/