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loopylist.java
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loopylist.java
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//program to check for loops in the list
import java.io.*;
import java.util.*;
class LinkedList
{ static Node head;
static class Node
{
int data;
Node next;
Node(int d)
{
data=d;
next=null;
}
}
public static void insert(int element)
{
Node n = new Node(element);
n.next=head;
head=n;
}
static boolean loop(Node h)
{
HashSet<Node> set = new HashSet<Node>(); //hashset prevents duplicacy
while(h!=null)
{
if(set.contains(h)) //if a node is alrdy present in the hashset
return true;
set.add(h);
h=h.next;
}
return false;
}
public static void main(String argd[])
{
LinkedList ll = new LinkedList();
ll.insert(10);
ll.insert(40);
ll.insert(45);
ll.insert(10);
//we delibrately make a loop to test the code
ll.head.next.next.next.next = ll.head;
if(loop(head))
System.out.println("Looped!! Trapped");
else
System.out.println("No loop!");
}
}