Query related to Single LinkedList?

As to identifying a loop in the list - you can check this (http://www.dev-archive.com/forum/showthread.php?t=416383&highlight=list) thread. See especially Yves M's post.
As for rectifying - if you don't somehow keep track of all nodes in the list then this is not possible since you can't track the rest of the list (after node 36). If you keep track of all nodes added to the list in another data structure, lets say a vector with pointers to all the nodes, or a hash table or a tree - then you can map all nodes that are ok - appear before the loop, identify the 1st node that has a backwards next pointer and point it to the node that is not pointed by any other node's next pointer (in your case, node 37).

Best of luck,

Zachm

we can use this code also to find loop in list.

t1= first;
t2 = first;
while(t2)
{
t2 = t2->next;
if( t2 == t1 )
break;
}
if(t2 != NULL)
std::cout<<std::endl<<"Your List contains loop !!"<<std::endl;

Complete program can be like this

#include <iostream>
#include <string>

struct node
{
int data;
node *next;
};
class TestClassList
{
node *front,*rear;
node *createnode(int n);
public:
TestClassList(){front = rear = NULL;}
void insertnode(int n);
void createloop(int n);
void checkloop();
};

node * TestClassList::createnode(int n)
{
node *temp = new node;
temp->data = n;
temp->next = NULL;
return temp;
}
void TestClassList::insertnode(int n)
{
if( front == NULL)
front = rear = createnode(n);
else
{
node *temp = rear;
rear = createnode(n);
temp->next = rear;
}
}

void TestClassList::createloop(int n)
{
node *t = front;
int i=1;
while(t && i < n)
{
t = t->next;
i++;
}
t->next = front;
}

void TestClassList::checkloop()
{
std::cout<<std::endl<<"Nodes in Loop are "<<std::endl;
node *t1,*t2;
t1=t2=front;
while(t2)
{
std::cout<<t2->data<<" ";
t2 = t2->next;
if(t2 == t1)
break;
}
if(t2 != NULL)
std::cout<<std::endl<<"Your List contains loop !!"<<std::endl;
}

int main()
{
TestClassList lo;
int i,n;
for(i=0;i<10;i++)
lo.insertnode(i);
lo.checkloop();
std::cout<<std::endl<<"Enter the node number from where you want to make loop : ";
std::cin>>n;
lo.createloop(n);
std::cout<<std::endl;
lo.checkloop();
return (1);
}

Output

//Nodes Before any Loop in your list
Nodes in Loop are
0 1 2 3 4 5 6 7 8 9

Enter the node number from where you want to make loop : 6

//Nodes After loop exist in your list
Nodes in Loop are
0 1 2 3 4 5
Your List contains loop !!

Press ENTER to continue.