Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Make a loop at k-th position in a linked list

  • Difficulty Level : Easy
  • Last Updated : 07 Dec, 2021

Given a linked list and a position k. Make a loop at k-th position
Examples: 

Input : Given linked list

Output : Modified linked list

 

Algorithm 
1) Traverse the first linked list till k-th point 
2) Make backup of the k-th node 
3) Traverse the linked linked list till end 
4) Attach the last node with k-th node 
 

C++




// CPP program for making loop at k-th index
// of given linked list
#include <bits/stdc++.h>
using namespace std;
 
/* Link list node */
struct Node {
    int data;
    struct Node* next;
};
 
/* Function to make loop at k-th elements of
linked list */
void makeloop(struct Node** head_ref, int k)
{
    // traverse the linked list until loop
    // point not found
    struct Node* temp = *head_ref;
    int count = 1;
    while (count < k) {
        temp = temp->next;
        count++;
    }
 
    // backup the joint point
    struct Node* joint_point = temp;
 
    // traverse remaining nodes
    while (temp->next != NULL)
        temp = temp->next;
 
    // joint the last node to k-th element
    temp->next = joint_point;
}
 
/* Function to push a node */
void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node =
        (struct Node*)malloc(sizeof(struct Node));
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}
 
/* Function to print linked list */
void printList(struct Node* head, int total_nodes)
{
    struct Node* curr = head;
    int count = 0;
    while (count < total_nodes) {
        count++;
        cout << curr->data << " ";
        curr = curr->next;
    }
}
 
int countNodes(Node *ptr)
{
    int count = 0;
    while (ptr != NULL)
    {
        ptr = ptr->next;
        count++;
    }
    return count;
}
 
/* Driver program to test above function*/
int main()
{
    // Create a linked list 1->2->3->4->5->6->7
    struct Node* head = NULL;
    push(&head, 7);
    push(&head, 6);
    push(&head, 5);
    push(&head, 4);
    push(&head, 3);
    push(&head, 2);
    push(&head, 1);
 
    // k should be less than the
    // numbers of nodes
    int k = 4;
    int total_nodes = countNodes(head);
 
    cout << "\nGiven list\n";
    printList(head, total_nodes);
 
    makeloop(&head, k);
 
    cout << "\nModified list\n";
    printList(head, total_nodes);
    return 0;
}

Java




// Java program for making loop at k-th index
// of given linked list
class GFG
{
     
// Link list node /
static class Node
{
    int data;
    Node next;
}
 
// Function to make loop at k-th elements of
//linked list /
static Node makeloop( Node head_ref, int k)
{
    // traverse the linked list until loop
    // point not found
    Node temp = head_ref;
    int count = 1;
    while (count < k)
    {
        temp = temp.next;
        count++;
    }
 
    // backup the joint point
    Node joint_point = temp;
 
    // traverse remaining nodes
    while (temp.next != null)
        temp = temp.next;
 
    // joint the last node to k-th element
    temp.next = joint_point;
    return head_ref;
}
 
// Function to push a node /
static Node push( Node head_ref, int new_data)
{
    Node new_node = new Node();
    new_node.data = new_data;
    new_node.next = (head_ref);
    (head_ref) = new_node;
    return head_ref;
}
 
// Function to print linked list /
static void printList( Node head, int total_nodes)
{
    Node curr = head;
    int count = 0;
    while (count < total_nodes)
    {
        count++;
        System.out.print(curr.data + " ");
        curr = curr.next;
    }
}
 
static int countNodes(Node ptr)
{
    int count = 0;
    while (ptr != null)
    {
        ptr = ptr.next;
        count++;
    }
    return count;
}
 
// Driver code
public static void main(String args[])
{
    // Create a linked list 1.2.3.4.5.6.7
    Node head = null;
    head = push(head, 7);
    head = push(head, 6);
    head = push(head, 5);
    head = push(head, 4);
    head = push(head, 3);
    head = push(head, 2);
    head = push(head, 1);
 
    // k should be less than the
    // numbers of nodes
    int k = 4;
    int total_nodes = countNodes(head);
 
    System.out.print("\nGiven list\n");
    printList(head, total_nodes);
 
    head = makeloop(head, k);
 
    System.out.print( "\nModified list\n");
    printList(head, total_nodes);
}
}
 
// This code is contributed by Arnab Kundu

Python3




# Python3 program for making loop at k-th index
# of given linked list
import math
 
# Link list node
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
 
# Function to make loop at k-th elements of
#linked list
def makeloop(head_ref, k):
     
    # traverse the linked list until loop
    # point not found
    temp = head_ref
    count = 1
    while (count < k):
        temp = temp.next
        count = count + 1
 
    # backup the joint point
    joint_point = temp
 
    # traverse remaining nodes
    while (temp.next != None):
        temp = temp.next
 
    # joint the last node to k-th element
    temp.next = joint_point
    return head_ref
 
# Function to push a node
def push(head_ref, new_data):
    new_node = Node(new_data)
    new_node.data = new_data
    new_node.next = head_ref
    head_ref = new_node
    return head_ref
 
# Function to print linked list
def printList( head,total_nodes):
    curr = head
    count = 0
    while (count < total_nodes):
        count = count + 1
        print(curr.data, end = " ")
        curr = curr.next
     
def countNodes(ptr):
    count = 0
    while (ptr != None):
        ptr = ptr.next
        count = count + 1
     
    return count
 
# Driver Code
if __name__=='__main__':
     
    # Create a linked list 1.2.3.4.5.6.7
    head = None
    head = push(head, 7)
    head = push(head, 6)
    head = push(head, 5)
    head = push(head, 4)
    head = push(head, 3)
    head = push(head, 2)
    head = push(head, 1)
 
    # k should be less than the
    # numbers of nodes
    k = 4
    total_nodes = countNodes(head)
 
    print("Given list")
    printList(head, total_nodes)
 
    makeloop(head, k)
 
    print("\nModified list")
    printList(head, total_nodes)
     
# This code is contributed by Srathore

C#




// C# program for making loop at k-th index
// of given linked list
using System;
 
class GFG
{
     
// Link list node /
public class Node
{
    public int data;
    public Node next;
}
 
// Function to make loop at k-th elements of
//linked list /
static Node makeloop( Node head_ref, int k)
{
    // traverse the linked list until loop
    // point not found
    Node temp = head_ref;
    int count = 1;
    while (count < k)
    {
        temp = temp.next;
        count++;
    }
 
    // backup the joint point
    Node joint_point = temp;
 
    // traverse remaining nodes
    while (temp.next != null)
        temp = temp.next;
 
    // joint the last node to k-th element
    temp.next = joint_point;
    return head_ref;
}
 
// Function to push a node /
static Node push( Node head_ref, int new_data)
{
    Node new_node = new Node();
    new_node.data = new_data;
    new_node.next = (head_ref);
    (head_ref) = new_node;
    return head_ref;
}
 
// Function to print linked list /
static void printList( Node head, int total_nodes)
{
    Node curr = head;
    int count = 0;
    while (count < total_nodes)
    {
        count++;
        Console.Write(curr.data + " ");
        curr = curr.next;
    }
}
 
static int countNodes(Node ptr)
{
    int count = 0;
    while (ptr != null)
    {
        ptr = ptr.next;
        count++;
    }
    return count;
}
 
// Driver code
public static void Main(String []args)
{
    // Create a linked list 1.2.3.4.5.6.7
    Node head = null;
    head = push(head, 7);
    head = push(head, 6);
    head = push(head, 5);
    head = push(head, 4);
    head = push(head, 3);
    head = push(head, 2);
    head = push(head, 1);
 
    // k should be less than the
    // numbers of nodes
    int k = 4;
    int total_nodes = countNodes(head);
 
    Console.Write("\nGiven list\n");
    printList(head, total_nodes);
 
    head = makeloop(head, k);
 
    Console.Write( "\nModified list\n");
    printList(head, total_nodes);
}
}
 
// This code contributed by Rajput-Ji

Javascript




<script>
// javascript program for making loop at k-th index
// of given linked list    
// Link list node /
class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}
 
    // Function to make loop at k-th elements of
    // linked list /
    function makeloop(head_ref , k) {
        // traverse the linked list until loop
        // point not found
var temp = head_ref;
        var count = 1;
        while (count < k) {
            temp = temp.next;
            count++;
        }
 
        // backup the joint point
var joint_point = temp;
 
        // traverse remaining nodes
        while (temp.next != null)
            temp = temp.next;
 
        // joint the last node to k-th element
        temp.next = joint_point;
        return head_ref;
    }
 
    // Function to push a node /
    function push(head_ref , new_data) {
var new_node = new Node();
        new_node.data = new_data;
        new_node.next = (head_ref);
        (head_ref) = new_node;
        return head_ref;
    }
 
    // Function to print linked list /
    function printList(head , total_nodes) {
var curr = head;
        var count = 0;
        while (count < total_nodes) {
            count++;
            document.write(curr.data + " ");
            curr = curr.next;
        }
    }
 
    function countNodes(ptr) {
        var count = 0;
        while (ptr != null) {
            ptr = ptr.next;
            count++;
        }
        return count;
    }
 
    // Driver code
     
        // Create a linked list 1.2.3.4.5.6.7
var head = null;
        head = push(head, 7);
        head = push(head, 6);
        head = push(head, 5);
        head = push(head, 4);
        head = push(head, 3);
        head = push(head, 2);
        head = push(head, 1);
 
        // k should be less than the
        // numbers of nodes
        var k = 4;
        var total_nodes = countNodes(head);
 
        document.write("<br/>Given list<br/>");
        printList(head, total_nodes);
 
        head = makeloop(head, k);
 
        document.write("<br/>Modified list<br/>");
        printList(head, total_nodes);
 
// This code contributed by umadevi9616
</script>

Output: 
 

Given list
1 2 3 4 5 6 7 
Modified list
1 2 3 4 5 6 7 

 

?list=PLqM7alHXFySH41ZxzrPNj2pAYPOI8ITe7
 


My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!