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

Recommended: Please solve it on PRACTICE first, before moving on to the solution.

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

C++

// 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; 
} 

Java

// 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 

Python3

    # Python3 program to construct a linked list 
# from given 2D matrix 
import math 
  
# struct node of linked list 
class Node:  
    def __init__(self, data):  
        self.data = data  
        self.right = None
        self.down = None
  
# returns head pointer of linked list 
# constructed from 2D matrix 
def construct(arr, i, j, m, n): 
      
    # return if i or j is out of bounds 
    if (i > n - 1 or j > m - 1): 
        return None
  
    # create a new node for current i and j 
    # and recursively allocate its down and 
    # right pointers 
    temp = Node(arr[i][j]) 
    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 
def display(head): 
      
    # pointer to move right 
    # Rp 
  
    # pointer to move down 
    Dp = head 
  
    # loop till node.down is not None 
    while (Dp): 
        Rp = Dp 
  
        # loop till node.right is not None 
        while (Rp): 
            print(Rp.data, end = " ") 
            Rp = Rp.right 
          
        print() 
        Dp = Dp.down 
      
# Driver Code 
if __name__=='__main__':  
    # 2D matrix 
    arr = [[ 1, 2, 3 ], 
           [ 4, 5, 6 ], 
           [ 7, 8, 9 ]] 
  
    m, n = 3, 3
    head = construct(arr, 0, 0, m, n) 
    display(head) 
      
# This code is contributed by AbhiThakur 

C#

// 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 */

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.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes

Recommended: Please solve it on PRACTICE first, before moving on to the solution.

C++

Java

Python3

C#

Recommended Posts: