static Node_no_constructor push(Node_no_constructor head_ref, int new_data)
{
// Allocate node
Node_no_constructor new_node = new Node_no_constructor();
// Put in the data
new_node.data = new_data;
new_node.flag = 0;
// Link the old list off the new node
new_node.next = head_ref;
// Move the head to point to the new node
head_ref = new_node;
return(head_ref);
}
// Returns true if there is a loop in linked
// list else returns false.
static bool detectLoop_1(Node_no_constructor h)
{
while (h != null)
{
// If this node is already traverse
// it means there is a cycle
// (Because you we encountering the
// node for the second time).
if (h.flag == 1)
{
return(true);
}
// If we are seeing the node for
// the first time, mark its flag as 1
h.flag = 1;
h = h.next;
}
return(false);
}
/* Driver code*/
public static void Main(String[] args)
{
DetectLoop llist = new DetectLoop();
llist.push(20);
llist.push(4);
llist.push(15);
llist.push(10);
/*Create loop for testing */
llist.head.next.next.next.next = llist.head;
if (detectLoop(llist.head))
{
Console.WriteLine("Loop found");
}
else
{
Console.WriteLine("No Loop");
}
/*
* Output
* Loop found
* Complexity Analysis:
*
* Time complexity: O(n).
* Only one traversal of the loop is needed.
* Auxiliary Space: O(n).
*
* n is the space required to store the value in hashmap.
*/
// Start with the empty list
Node_no_constructor head = null;
head = push(head, 20);
head = push(head, 4);
head = push(head, 15);
head = push(head, 10);
// Create a loop for testing
head.next.next.next.next = head;
if (detectLoop_1(head))
{
Console.Write("Loop found");
}
else
{
Console.Write("No Loop");
}
/*
* Output
* Loop found
* Complexity Analysis:
*
* Time complexity:O(n).
* Only one traversal of the loop is needed.
* Auxiliary Space:O(1).
*
* No extra space is needed.*/
}
