Introduction to Multi Linked List

A multi-linked list is a special type of list that contains two or more logical key sequences. Before checking details about multi-linked list, see what is a linked list. A linked list is a data structure that is free from any size restriction until the heap memory is not full. We have seen different types of linked lists, such as Singly Linked List, Circular Linked List, and Doubly Linked List. Here we will see about multi-linked list.

In a multi-linked list, each node can have N number of pointers to other nodes. A multi-linked list is generally used to organize multiple orders of one set of elements.

Properties of Multi-Linked List:

The properties of a multi-linked list are mentioned below.

• It is an integrated list of related structures.
• All the nodes are integrated using links of pointers.
• Linked nodes are connected with related data.
• Nodes contain pointers from one structure to the other.

Structure of Multi-linked list:

The structure of a multi-linked list depends on the structure of a node. A single node generally contains two things:

• A list of pointers
• All the relevant data.

 Shown below is the structure of a node that contains only one data and a list of pointers.

typedef struct node {
    int data;
    vector<struct node*> pointers;
} Node;

// This code is contributed by akashish__

typedef struct node {
    int data;
    vector<struct node*> pointers;
} Node;

/*package whatever //do not write package name here */

import java.io.*;

class GFG {
    public static void main(String[] args) {}
    public static class Node {
        int data;
        Node[] children;
    };
}

// This code is contributed by ishankhandelwal

# Python code
class Node:
    def _init_(self):
        self.data = 0
        self.pointers = []

        # This code is contributed by ishankhandelwals.

// C# code to create the structure of a node 

using System;

class GFG
{
    public static void Main() { }
    public class Node
    {
        int data;
        Node[] children;
    };
}

// This code is contributed by Saurabh jaiswal

// JS code 
class node{

    constructor(){
        this.data;
        this.pointers=[];
    }
}

// This code is contributed by ishankhandelwals.

Use cases of Multi-Linked Lists:

Some use cases of a multi-linked list are:

• Multiple orders of one set of elements
• Representation of a sparse matrix
• List of List

Multiple orders of one set of elements:

• A multi-linked list is a more general linked list with multiple links from nodes. 
• For example, suppose the task is to maintain a list in multiple orders, age and name here, we can define a Node that has two references, an age pointer and a name pointer. 
• Then it is possible to maintain one list, where if we follow the name pointer we can traverse the list in alphabetical order 
• And if we try to traverse the age pointer, we can traverse the list by age also.
• This type of node organization may be useful for maintaining a customer list in a bank where the same list can be traversed in any order (name, age, or any other criteria) based on the need. For example, suppose my elements include the name of a person and his/her age. e.g.

(ANIMESH, 19), (SUMIT, 17), (HARDIK, 22), (ISHA, 18)

Inserting into this structure is very much like inserting the same node into two separate lists. In multi-linked lists it is quite common to have back-pointers, i.e. inverses of each of the forward links; in the above example, this would mean that each node had 4pointers.

Representation of Sparse Matrix:

Multi Linked Lists are used to store sparse matrices. A sparse matrix is such a matrix that has few non-zero values. If we use a normal array to store such a matrix, it will end up wasting lots of space.

The sparse matrix can be represented by using a linked list for every row and column. 

• A node in a multi-linked list has four parts: 
  • The first part stores the data. 
  • The second stores the pointer to the next row.
  • Third for the pointer to the next column and 
  • Fourth for storing the coordinate number of the cell in the matrix.

List of List:

A multi-linked list can be used to represent a list of lists. For example, we can create a linked list where each node is itself a list and have pointers to other nodes. 
See the structure below:

• It is a 2-dimensional data structure.
• Here each node has three fields:
  • The first field stores the data.
  • The second field stores a pointer to the child node.
  • The third field stores the pointer to the next node.

Advantages of Multi-Linked List:

The advantages of a multi-linked list are:

• Sets of same data can be processed into multiple sequences.
• Data are not duplicated anywhere.
• Data of one kind exist only once in the list.

Comparison of Multi-Linked List with Doubly Linked List:

Let's first see the structure of a node of Doubly Linked List:

#include <iostream>
using namespace std;

typedef struct node {
    int data;
    struct node* prev;
    struct node* next;
} Node;

int main() {

    return 0;
}

// This code is contributed by akashish__

typedef struct node {
    int data;
    struct node* prev;
    struct node* next;
} Node;

/*package whatever //do not write package name here */

import java.io.*;

class GFG {
    public static void main(String[] args) {}
    public static class Node {
        int data;
        Node prev;
        Node next;
    };
}

// This code is contributed by ishankhandelwal

# Python code
class Node:
  def _init_(self, val = 0, next = None):
    self.val = val
    self.next = next
    
# This code is contributed by lokesh.

using System;

public class GFG{

   static public void Main (){}
   public class Node {
        int data;
        Node prev;
        Node next;
    };
} 

// This code is contributed by aadityapburujwale

// JS code for above approach
class Node{
    constructor(){
        this.data;
        this.prev=null;
        this.next=null;
    }
}

// This code is contributed by ishankhandelwals.

Comparing Doubly linked list and Multi-linked list:

• Unlike doubly nodes in a multilinked list may or may not have an inverse for each pointer.
• A doubly Linked list has exactly two pointers, whether multi-linked list can have multiple pointers
• In a doubly linked list, pointers are exactly opposite to each other, but in a multi-linked list, it is not so.
• Doubly linked list is a special case of multi-linked list.