Convert a Singly Linked List to an array

Difficulty Level : Easy
Last Updated : 19 Aug, 2021

Given a singly linked list and the task is to convert it into an array.
Examples:

Input: List = 1 -> 2 -> 3 -> 4 -> 5 -> NULL
Output: 1 2 3 4 5
Input: List = 10 -> 20 -> 30 -> 40 -> 50 -> NULL
Output: 10 20 30 40 50

Approach: An approach to creating a linked list from the given array has been discussed in this article. Here, an approach to convert the given linked list to an array will be discussed.

Find the length of the given linked list say len.
Create an array of size len.
Traverse the given linked list and store the elements in the array one at a time.

Below is the implementation of the above approach:

C++

// C++ implementation of the approach
#include <iostream>
using namespace std;
 
// Singly Linked List structure
struct node {
    int data;
    node* next;
};
 
// Function to add a new node
// to the Linked List
node* add(int data)
{
    node* newnode = new node;
    newnode->data = data;
    newnode->next = NULL;
    return newnode;
}
 
// Function to print the array contents
void printArr(int a[], int n)
{
    for (int i = 0; i < n; i++)
        cout << a[i] << " ";
}
 
// Function to return the length
// of the Linked List
int findlength(node* head)
{
    node* curr = head;
    int cnt = 0;
    while (curr != NULL) {
        cnt++;
        curr = curr->next;
    }
    return cnt;
}
 
// Function to convert the
// Linked List to an array
void convertArr(node* head)
{
 
    // Find the length of the
    // given linked list
    int len = findlength(head);
 
    // Create an array of the
    // required length
    int arr[len];
 
    int index = 0;
    node* curr = head;
 
    // Traverse the Linked List and add the
    // elements to the array one by one
    while (curr != NULL) {
        arr[index++] = curr->data;
        curr = curr->next;
    }
 
    // Print the created array
    printArr(arr, len);
}
 
// Driver code
int main()
{
    node* head = NULL;
    head = add(1);
    head->next = add(2);
    head->next->next = add(3);
    head->next->next->next = add(4);
    head->next->next->next->next = add(5);
 
    convertArr(head);
 
    return 0;
}

Java

// Java implementation of the approach
class GFG
{
 
// Singly Linked List structure
static class node
{
    int data;
    node next;
}
 
// Function to add a new node
// to the Linked List
static node add(int data)
{
    node newnode = new node();
    newnode.data = data;
    newnode.next = null;
    return newnode;
}
 
// Function to print the array contents
static void printArr(int a[], int n)
{
    for (int i = 0; i < n; i++)
        System.out.print(a[i]+" ");
}
 
// Function to return the length
// of the Linked List
static int findlength(node head)
{
    node curr = head;
    int cnt = 0;
    while (curr != null)
    {
        cnt++;
        curr = curr.next;
    }
    return cnt;
}
 
// Function to convert the
// Linked List to an array
static void convertArr(node head)
{
 
    // Find the length of the
    // given linked list
    int len = findlength(head);
 
    // Create an array of the
    // required length
    int []arr = new int[len];
 
    int index = 0;
    node curr = head;
 
    // Traverse the Linked List and add the
    // elements to the array one by one
    while (curr != null) 
    {
        arr[index++] = curr.data;
        curr = curr.next;
    }
 
    // Print the created array
    printArr(arr, len);
}
 
// Driver code 
public static void main(String []args)
{
    node head = new node();
    head = add(1);
    head.next = add(2);
    head.next.next = add(3);
    head.next.next.next = add(4);
    head.next.next.next.next = add(5);
 
    convertArr(head);
}
}
 
// This code is contributed by Rajput-Ji

Python3

# Pytho3 implementation of the approach
 
# Structure of a Node 
class node: 
    def __init__(self, data): 
        self.data = data 
        self.next = None
 
# Function to add a new node
# to the Linked List
def add(data):
 
    newnode = node(0)
    newnode.data = data
    newnode.next = None
    return newnode
 
# Function to print the array contents
def printArr(a, n):
 
    i = 0
    while(i < n):
        print (a[i], end = " ")
        i = i + 1
 
# Function to return the length
# of the Linked List
def findlength( head):
 
    curr = head
    cnt = 0
    while (curr != None):
     
        cnt = cnt + 1
        curr = curr.next
     
    return cnt
 
# Function to convert the
# Linked List to an array
def convertArr(head):
 
    # Find the length of the
    # given linked list
    len1 = findlength(head)
 
    # Create an array of the
    # required length
    arr = []
 
    index = 0
    curr = head
 
    # Traverse the Linked List and add the
    # elements to the array one by one
    while (curr != None): 
        arr.append( curr.data)
        curr = curr.next
     
    # Print the created array
    printArr(arr, len1)
 
# Driver code 
head = node(0)
head = add(1)
head.next = add(2)
head.next.next = add(3)
head.next.next.next = add(4)
head.next.next.next.next = add(5)
convertArr(head)
 
# This code is contributed by Arnab kundu

C#

// C# implementation of the approach
using System;
                     
class GFG
{
 
// Singly Linked List structure
public class node
{
    public int data;
    public node next;
}
 
// Function to add a new node
// to the Linked List
static node add(int data)
{
    node newnode = new node();
    newnode.data = data;
    newnode.next = null;
    return newnode;
}
 
// Function to print the array contents
static void printArr(int []a, int n)
{
    for (int i = 0; i < n; i++)
        Console.Write(a[i] + " ");
}
 
// Function to return the length
// of the Linked List
static int findlength(node head)
{
    node curr = head;
    int cnt = 0;
    while (curr != null)
    {
        cnt++;
        curr = curr.next;
    }
    return cnt;
}
 
// Function to convert the
// Linked List to an array
static void convertArr(node head)
{
 
    // Find the length of the
    // given linked list
    int len = findlength(head);
 
    // Create an array of the
    // required length
    int []arr = new int[len];
 
    int index = 0;
    node curr = head;
 
    // Traverse the Linked List and add the
    // elements to the array one by one
    while (curr != null) 
    {
        arr[index++] = curr.data;
        curr = curr.next;
    }
 
    // Print the created array
    printArr(arr, len);
}
 
// Driver code 
public static void Main(String []args)
{
    node head = new node();
    head = add(1);
    head.next = add(2);
    head.next.next = add(3);
    head.next.next.next = add(4);
    head.next.next.next.next = add(5);
 
    convertArr(head);
}
}
 
// This code is contributed by 29AjayKumar

Javascript

<script>
 
// JavaScript implementation of the approach
 
// Singly Linked List structure
class node {
        constructor() {
                this.data = 0;
                this.next = null;
             }
        }
         
// Function to add a new node
// to the Linked List
function add( data)
{
    var newnode = new node();
    newnode.data = data;
    newnode.next = null;
    return newnode;
}
 
// Function to print the array contents
function printArr( a,  n)
{
    for (let i = 0; i < n; i++)
        document.write(a[i]+" ");
}
 
// Function to return the length
// of the Linked List
function findlength( head)
{
    var curr = head;
    let cnt = 0;
    while (curr != null)
    {
        cnt++;
        curr = curr.next;
    }
    return cnt;
}
 
// Function to convert the
// Linked List to an array
function convertArr( head)
{
 
    // Find the length of the
    // given linked list
    let len = findlength(head);
 
    // Create an array of the
    // required length
    let arr = new Array(len);
     
    let index = 0;
    var curr = head;
 
    // Traverse the Linked List and add the
    // elements to the array one by one
    while (curr != null)
    {
        arr[index++] = curr.data;
        curr = curr.next;
    }
 
    // Print the created array
    printArr(arr, len);
}
 
// Driver Code
 
var head = new node();
head = add(1);
head.next = add(2);
head.next.next = add(3);
head.next.next.next = add(4);
head.next.next.next.next = add(5);
 
convertArr(head);
     
</script>

Output:

1 2 3 4 5

Time Complexity: O(N)
Auxiliary Space: O(N)

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Table of Contents

Convert a Singly Linked List to an array

C++

Java

Python3

C#

Javascript

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