Convert a Singly Linked List to an array

Last Updated : 04 Sep, 2024

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

Examples:

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

Approach:

The idea is to iterate through the linked list and for each node add its value into the array.

C++

// C++ code to convert a Singly Linked List to an array

#include <bits/stdc++.h>
using namespace std;

class Node {
public:
    int data;
    Node* next;
    Node(int data) {
        this->data = data;
        this->next = nullptr;
    }
};

// Function to convert a singly linked list to an array
vector<int> linkedListToArray(Node* head) {
    vector<int> arr;
    Node* curr = head;

    while (curr != nullptr) {
        arr.push_back(curr->data);
        curr = curr->next;
    }

    return arr;
}

void printArray(const vector<int>& arr) {
    for (int i = 0; i < arr.size(); i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

int main() {
    // Create a hardcoded singly linked list: 1 -> 2 -> 3 -> 4
    Node* head = new Node(1);
    head->next = new Node(2);
    head->next->next = new Node(3);
    head->next->next->next = new Node(4);

    vector<int> arr = linkedListToArray(head);
    printArray(arr);

    return 0;
}

// C code to convert a Singly Linked List to an array

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* next;
};

// Function to convert a singly linked list to an array
void linkedListToArray(struct Node* head, int arr[], int* size) {
    int count = 0;
    struct Node* curr = head;

    // Traverse the linked list and fill the array
    while (curr != NULL) {
        arr[count] = curr->data;
        count++;
        curr = curr->next;
    }

    *size = count; 
}

void printArray(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

struct Node* createNode(int data) {
    struct Node* newNode =
      (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->next = NULL;
    return newNode;
}

int main() {
    // Create a hardcoded singly linked list: 1 -> 2 -> 3 -> 4
    struct Node* head = createNode(1);
    head->next = createNode(2);
    head->next->next = createNode(3);
    head->next->next->next = createNode(4);

    int arr[1000]; 
    int size;
    
    linkedListToArray(head, arr, &size);
    printArray(arr, size);

    return 0;
}

Java

// Java code to convert a Singly Linked List to an array

import java.util.ArrayList;

class Node {
    int data;
    Node next;
    Node(int data)
    {
        this.data = data;
        this.next = null;
    }
}

class GfG {

    // Function to convert a singly linked list to an array
    static ArrayList<Integer> linkedListToArray(Node head)
    {
        ArrayList<Integer> arr = new ArrayList<>();
        Node curr = head;

        while (curr != null) {
            arr.add(curr.data);
            curr = curr.next;
        }

        return arr;
    }

    static void printArray(ArrayList<Integer> arr)
    {
        for (int i = 0; i < arr.size(); i++) {
            System.out.print(arr.get(i) + " ");
        }
        System.out.println();
    }

    public static void main(String[] args)
    {
        // Create a hardcoded singly linked list: 1 -> 2 ->
        // 3 -> 4
        Node head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(3);
        head.next.next.next = new Node(4);

        ArrayList<Integer> arr = linkedListToArray(head);
        printArray(arr);
    }
}

Python

# Python code to convert a Singly Linked List to an array

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

# Function to convert a singly linked list to an array
def linked_list_to_array(head):
    arr = []
    curr = head

    while curr is not None:
        arr.append(curr.data)
        curr = curr.next

    return arr

# Function to print an array
def print_array(arr):
    for i in arr:
        print(i, end=" ")
    print()

if __name__ == "__main__":
    # Create a hardcoded singly linked list: 1 -> 2 -> 3 -> 4
    head = Node(1)
    head.next = Node(2)
    head.next.next = Node(3)
    head.next.next.next = Node(4)

    arr = linked_list_to_array(head)
    print_array(arr)

// C# code to convert a Singly Linked List to an array

using System;
using System.Collections.Generic;

class Node {
    public int data;
    public Node next;

    public Node(int data)
    {
        this.data = data;
        this.next = null;
    }
}

class GfG {

    // Function to convert a singly linked list to an array
    public static List<int> LinkedListToArray(Node head)
    {
        List<int> arr = new List<int>();
        Node curr = head;

        while (curr != null) {
            arr.Add(curr.data);
            curr = curr.next;
        }

        return arr;
    }

    public static void PrintArray(List<int> arr)
    {
        for (int i = 0; i < arr.Count; i++) {
            Console.Write(arr[i] + " ");
        }
        Console.WriteLine();
    }

    static void Main()
    {
        // Create a hardcoded singly linked list: 1 -> 2 ->
        // 3 -> 4
        Node head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(3);
        head.next.next.next = new Node(4);

        List<int> arr = LinkedListToArray(head);
        PrintArray(arr);
    }
}

JavaScript

// Javascript code to convert a Singly Linked List to an
// array

class Node {
    constructor(data)
    {
        this.data = data;
        this.next = null;
    }
}

// Function to convert a singly linked list to an array
function linkedListToArray(head)
{
    const arr = [];
    let curr = head;

    while (curr !== null) {
        arr.push(curr.data);
        curr = curr.next;
    }

    return arr;
}

function printArray(arr)
{
    for (let i = 0; i < arr.length; i++) {
        console.log(arr[i]);
    }
}

// Create a hardcoded singly linked list: 1 -> 2 -> 3 -> 4
const head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);

const arr = linkedListToArray(head);
printArray(arr);

Output

1 2 3 4

Time Complexity: O(n)
Auxiliary Space: O(1)

Convert a Singly Linked List to an array

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