Data-Structures/loopnodes.java at master · ishitasinghal/Data-Structures · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
//program to check for loops and count them in the list
importjava.io.*;
importjava.util.*;
classLinkedList
{
staticclassNode
	{
intdata;
Nodenext;
Node(intd)
 {
data=d;
next=null;
 }
	}

staticintcount(Noden)
	{
inttot=1;
Nodetemp = n;
while(temp.next != n)
 {
tot++;
temp=temp.next;
 }
returntot;
	}

staticintnodesinloop(Nodeno)
	{
Nodeptr1 = no, ptr2=no;
while(ptr1!=null && ptr2!=null && ptr2!=null)
 {
ptr1 = ptr1.next; //moves a single node ahead
ptr2 = ptr2.next.next; //moves two nodes ahead

//if both meet at the same point then there is a loop
if(ptr1==ptr2)
 {
returncount(ptr1);
 }
 }
return0;
	}

staticNodenewnode(intelement)
	{
Nodet = newNode(element);
returnt;
	}
publicstaticvoidmain(Stringargd[])
	{
Nodehead = newnode(1);
head.next = newnode(2);
head.next.next = newnode(3);
head.next.next.next = newnode(4);
head.next.next.next.next = newnode(5);
head.next.next.next.next.next = newnode(6);


//we delibrately make a loop to test the code
head.next.next.next.next = head.next;
System.out.println(nodesinloop(head));
//let's try making another loop!
head.next.next.next.next.next = head.next;
System.out.println(nodesinloop(head));

	}
}