Create a Circular List Structure For Given Value K Using Recursion

// C# program to recursively create
// loopy linked list with four
// pointer left, right, up, down
// by given value K without using
// array of pointer and 2D matrix
using System;

class GFG{

// Struct node of circular linked
// list with four pointer
// next, prev, up, down
class Node
{
    public int data;
    public Node left;
    public Node right;
    public Node up;
    public Node down;
};

// Function to create a new node
static Node createNode(int value)
{
    Node temp = new Node();
    temp.data = value;
    temp.left = null;
    temp.right = null;
    temp.up = null;
    temp.down = null;
    
    return temp;
}

// Function to create Singly list
// whose nodes are connected with
// right pointer
static Node createListWithRightPointer(int k,
                                       int i)
{
    if (i > k)
        return null;
    Node node = createNode(i);
    
    // Recursively call the function to
    // create list with the right pointer
    node.right = createListWithRightPointer(k, 
                                            i + 1);
    return node;
}

// Function to create the k singly
// linked list and first node of
// each list is connected with
// down pointer
static Node createKsinglyList(int k)
{
    int rNum = 1;
    int limit = k;
    
    Node head = null;
    Node rowPointer = null;
    
    // Loop to create the k singly list
    // for each list first node points
    // to its below node by down pointer
    for(int i = 1; i <= k; i++) 
    {
       Node templist =createListWithRightPointer(limit, 
                                                 rNum);
       if (head == null)
       {
           head = templist;
           rowPointer = head;
       }
       else
       {
           rowPointer.down = templist;
           rowPointer = rowPointer.down;
       }
       rNum = rNum + k;
       limit = limit + k;
    }
    return head;
}

// Function to merge all list with
// level wise via down pointer
static void mergeKListWithDownPointer(Node head)
{
    Node first = null;
    Node second = null;
    Node start = head;
    first = start;
    second = first.down;
    
    // Run while loop to merge k list
    // row wise with down pointer
    while (second != null)
    {
        while (first != null || second != null)
        {
            first.down = second;
            first = first.right;
            second = second.right;
        }
        first = start.down;
        second = first.down;
        start = start.down;
    }
}

// Function to create the loop
// for each column
static void createLoopForEachColumn(Node head)
{
    Node first = null;
    Node last = null;
    first = head;
    last = first;
    
    while (last.down != null)
    {
        last = last.down;
    }
    
    // Run while loop to create
    // loop for each column
    while (first != null || last != null)
    {
        last.down = first;
        first = first.right;
        last = last.right;
    }
}

// Function to create the loop
// for each row
static void createLoopForEachRow(Node head)
{
    Node first = null;
    Node last = null;
    Node start = null;
    start = head;
    first = head;
    last = first;
    
    while (last.right != null)
    {
        last = last.right;
    }
    
    // Run while loop to create
    // loop for each row
    while (first.down != start) 
    {
        last.right = first;
        first = first.down;
        last = last.down;
    }
    last.right = first;
}

// Function to display the structure
// of the list
static void display(Node head)
{
    
    // Pointer to move right
    Node rPtr;

    // Pointer to move down
    Node dPtr = head;

    // Pointer to stop printing
    Node start = head;

    // Loop till node.down is not null
    while (dPtr.down != start)
    {
        rPtr = dPtr;

        // Loop till node.right is
        // not null
        while (rPtr.right != dPtr)
        {
            Console.Write(rPtr.data + " ");
            rPtr = rPtr.right;
        }
        Console.Write(rPtr.data + " ");
        Console.Write("\n");
        
        dPtr = dPtr.down;
    }
    rPtr = dPtr;

    // Loop till node.right is 
    // not null
    while (rPtr.right != dPtr) 
    {
        Console.Write(rPtr.data + " ");
        rPtr = rPtr.right;
    }
    Console.Write(rPtr.data + " ");
    Console.Write("\n");
}

static void createLoopInList(int k)
{
    
    // Create k singly Linked List each
    // first node of all list contain
    // address of it's below first node
    Node head = createKsinglyList(k);
    
    mergeKListWithDownPointer(head);
    createLoopForEachColoumn(head);
    
    createLoopForEachRow(head);
    display(head);
}

// Driver code
public static void Main(String[] args)
{
    int K = 4;
    
    // Create the list structure
    createLoopInList(K);
}
}

// This code is contributed by 29AjayKumar