Circular linked list

#1

Pls check my code from the line 37 to 52. code is at the link https://ide.codingblocks.com/s/233769 . I am unable to make the cycle in the linked list. It is showing runtime error.

#2 
void makeCycle(node *&head){
	node *i=head;
	node *prev;
	while(i!=NULL){
		node *j=head;
		while(j!=i){
			if(j->data==i->data){
				prev->next=j;  
				return;
			}
			j=j->next;
		}
		prev=i;
		i=i->next;
	}
}

prev is not initialized it contains garbage’
and you are writing prev->next
hence it give runtime error

but where you want to make cycle? at end ??

#3

we are given input like 1 2 3 4 5 2 3 -1
So we have to make a cycle from 5 to 2 because after 5 , 2 and 3 are repeating. So we have to make a cycle. And I have initialized prev in the lower part of the outer for loop. Prev-> next should not give an error here. Even if I am initializing prev with head, it is giving the same error.

#4

if you intialize the prev then it should not give error
as in first iteration
i=head;
j=head;
so inner while loop condition hold true
and inside it if is also true
so prev->next =j
and then you return

modify your logic