Construct a linked list from 2D matrix

Given a matrix. Convert it into a linked list matrix such that each node is connected to its next right and down node.

Example:

Input : 2D matrix 
1 2 3
4 5 6
7 8 9

Output :
1 -> 2 -> 3 -> NULL
|    |    |
v    v    v
4 -> 5 -> 6 -> NULL
|    |    |
v    v    v
7 -> 8 -> 9 -> NULL
|    |    |
v    v    v
NULL NULL NULL

Question Source : Factset Interview Experience | Set 9



The idea is to construct a new node for every element of matrix and recursively create its down and right nodes.

C++

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// CPP program to construct a linked list
// from given 2D matrix
#include <bits/stdc++.h>
using namespace std;
  
// struct node of linked list
struct Node {
    int data;
    Node* right, *down;
};
  
// returns head pointer of linked list
// constructed from 2D matrix
Node* construct(int arr[][3], int i, int j, 
                              int m, int n)
{
    // return if i or j is out of bounds
    if (i > n - 1 || j > m - 1)
        return NULL;
  
    // create a new node for current i and j
    // and recursively allocate its down and
    // right pointers
    Node* temp = new Node();
    temp->data = arr[i][j];
    temp->right = construct(arr, i, j + 1, m, n);
    temp->down  = construct(arr, i + 1, j, m, n);
    return temp;
}
  
// utility function for displaying
// linked list data
void display(Node* head)
{
    // pointer to move right
    Node* Rp;
  
    // pointer to move down
    Node* Dp = head;
  
    // loop till node->down is not NULL
    while (Dp) {
        Rp = Dp;
  
        // loop till node->right is not NULL
        while (Rp) {
            cout << Rp->data << " ";
            Rp = Rp->right;
        }
        cout << "\n";
        Dp = Dp->down;
    }
}
  
// driver program
int main()
{
    // 2D matrix
    int arr[][3] = {
        { 1, 2, 3 },
        { 4, 5, 6 },
        { 7, 8, 9 }
    };
  
    int m = 3, n = 3;
    Node* head = construct(arr, 0, 0, m, n);
    display(head);
    return 0;
}

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Java














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// Java program to construct a linked list 


// from given 2D matrix 


public class Linked_list_2D_Matrix { 


  


    // node of linked list 


    static class Node { 


        int data; 


        Node right; 


        Node down; 


    }; 


  


    // returns head pointer of linked list 


    // constructed from 2D matrix 


    static Node construct(int arr[][], int i, int j,  


                                     int m, int n) { 


          


        // return if i or j is out of bounds 


        if (i > n - 1 || j > m - 1) 


            return null; 


  


        // create a new node for current i and j 


        // and recursively allocate its down and 


        // right pointers 


        Node temp = new Node(); 


        temp.data = arr[i][j]; 


        temp.right = construct(arr, i, j + 1, m, n); 


        temp.down = construct(arr, i + 1, j, m, n); 


        return temp; 


    } 


  


    // utility function for displaying 


    // linked list data 


    static void display(Node head) { 


          


        // pointer to move right 


        Node Rp; 


  


        // pointer to move down 


        Node Dp = head; 


  


        // loop till node->down is not NULL 


        while (Dp != null) { 


            Rp = Dp; 


  


            // loop till node->right is not NULL 


            while (Rp != null) { 


                System.out.print(Rp.data + " "); 


                Rp = Rp.right; 


            } 


            System.out.println(); 


            Dp = Dp.down; 


        } 


    } 


  


    // driver program 


    public static void main(String args[]) { 


        // 2D matrix 


        int arr[][] = { { 1, 2, 3 },  


                        { 4, 5, 6 },  


                       { 7, 8, 9 } }; 


  


        int m = 3, n = 3; 


        Node head = construct(arr, 0, 0, m, n); 


        display(head); 


    } 


  


} 


// This code is contributed by Sumit Ghosh 



















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C#














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// C# program to construct a linked list 


// from given 2D matrix 


using System; 


      


public class Linked_list_2D_Matrix 


{ 


  


    // node of linked list 


    public class Node  


    { 


        public int data; 


        public Node right; 


        public Node down; 


    }; 


  


    // returns head pointer of linked list 


    // constructed from 2D matrix 


    static Node construct(int [,]arr, int i, int j,  


                                    int m, int n)  


    { 


          


        // return if i or j is out of bounds 


        if (i > n - 1 || j > m - 1) 


            return null; 


  


        // create a new node for current i and j 


        // and recursively allocate its down and 


        // right pointers 


        Node temp = new Node(); 


        temp.data = arr[i, j]; 


        temp.right = construct(arr, i, j + 1, m, n); 


        temp.down = construct(arr, i + 1, j, m, n); 


        return temp; 


    } 


  


    // utility function for displaying 


    // linked list data 


    static void display(Node head) 


    { 


          


        // pointer to move right 


        Node Rp; 


  


        // pointer to move down 


        Node Dp = head; 


  


        // loop till node->down is not NULL 


        while (Dp != null)  


        { 


            Rp = Dp; 


  


            // loop till node->right is not NULL 


            while (Rp != null)  


            { 


                Console.Write(Rp.data + " "); 


                Rp = Rp.right; 


            } 


            Console.WriteLine(); 


            Dp = Dp.down; 


        } 


    } 


  


    // Driver program 


    public static void Main()  


    { 


        // 2D matrix 


        int [,]arr = { { 1, 2, 3 },  


                        { 4, 5, 6 },  


                    { 7, 8, 9 } }; 


  


        int m = 3, n = 3; 


        Node head = construct(arr, 0, 0, m, n); 


        display(head); 


    } 


} 


  


/* This code contributed by PrinciRaj1992 */



















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Output:


1 2 3 
4 5 6 
7 8 9



This article is contributed by Mandeep Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.


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