Introduction to Doubly Linked List.cpp

//{ Driver Code Starts
// Initial Template for C++

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

class Node
{
public:
    Node *prev;
    int data;
    Node *next;

    Node()
    {
        prev = NULL;
        data = 0;
        next = NULL;
    }

    Node(int value)
    {
        prev = NULL;
        data = value;
        next = NULL;
    }
};

// } Driver Code Ends
// User function Template for C++

/*
class Node{
public:
    Node* prev;
    int data;
    Node* next;

    Node()
    {
        prev = NULL;
        data = 0;
        next = NULL;
    }

    Node(int value)
    {
        prev = NULL;
        data = value;
        next = NULL;
    }
};*/

class Solution
{
public:
    Node *constructDLL(vector<int> &arr)
    {
        Node *head = new Node(arr[0]);
        Node *temp = head;

        for (int i = 1; i < arr.size(); i++)
        {
            Node *n = new Node(arr[i]);
            temp->next = n;
            n->prev = temp;
            temp = n;
        }
        return head;
    }
};

//{ Driver Code Starts.

int main()
{
    int t;
    cin >> t;
    while (t--)
    {
        int n;
        cin >> n;
        vector<int> arr(n);
        for (int i = 0; i < n; i++)
            cin >> arr[i];
        Solution obj;
        Node *ans = obj.constructDLL(arr);
        while (ans)
        {
            cout << ans->data << " ";
            ans = ans->next;
        }
        cout << "\n";
    }
    return 0;
}

// } Driver Code Ends