Copy Constructor and Linked List

A copy constructor is just like a constructor; it is a member function that is used to initialize a value to an object with the help of another object in the same class. It is easier to use in the C++ programming language when there are several object parameters in the class.

The variables of a Linked list object have been dynamically allocated, then it is required to do a Deep Copy in order to create a copy of the object. Refer to “Shallow Copy and Deep Copy in C++” to know more about it.

For using a copy constructor in the linked list:

We have used a class Node to create the node of the linked list. A class with the name linkedlist is used here.
The private part will contain the variables of a pointer-type head and a tail.
A normal constructor assigns the values to the head and tail parts in the public part and a copy constructor is used to initialize a linked list object with the existing ones.

Below is the implementation of copy constructor.

C++

// A complete working C++ program to
// initialize linked list with Copy
// constructor
 
#include <bits/stdc++.h>
using namespace std;
 
// A linked list node
class Node {
public:
    int data;
    Node* next;
    Node(int x)
    {
        data = x;
        next = NULL;
    }
};
 
// A linked list class
class linkedlist {
 
private:
    // head and tail pointer of Node
    Node* head = NULL;
    Node* tail = NULL;
 
public:
    // Non-parameterized constructor
    linkedlist() { head = tail = NULL; }
 
    // Copy constructor to copy the data
    // members of one list into another
    linkedlist(const linkedlist& list)
    {
        if (list.head == NULL) {
            head = tail = NULL;
            return;
        }
 
        // Make a Node pointer temp and
        // initialize it to the head of list
        Node* temp = list.head;
 
        // This loop is creating the new
        // linked list by copying the
        // data of list
        while (temp != NULL) {
            Node* newNode = new Node(temp->data);
 
            if (head == NULL) {
                head = newNode;
                tail = newNode;
            }
            else {
                tail->next = newNode;
                tail = newNode;
            }
            temp = temp->next;
        }
    }
 
    // This function insert create a node
    // with given value and inserts the
    // node at the end of linked list
    void insert(int x)
    {
        // Allocate the temp Node and
        // put x as data into it
        Node* temp = new Node(x);
 
        // Check if the head is NULL
        if (head == NULL) {
            head = temp;
            return;
        }
        else {
            Node* t = head;
            while (t->next != NULL) {
                t = t->next;
            }
            t->next = temp;
        }
    }
 
    // This function prints contents of
    // linked list starting from head
    void print()
    {
        if (head == NULL) {
            cout << "List is empty" << endl;
            return;
        }
        Node* temp = head;
        while (temp != NULL) {
            cout << temp->data << " ";
            temp = temp->next;
        }
        cout << endl;
    }
};
 
// Driver code
int main()
{
    // Creating object l1 of linked list
    linkedlist l1;
 
    l1.insert(1);
    l1.insert(9);
    l1.insert(5);
    l1.insert(7);
 
    cout << "linked list l1 are: ";
    l1.print();
 
    // Copying l1 into l2
    linkedlist l2 = l1;
    cout << "linked list l2 are: ";
    l2.print();
 
    return 0;
}

Java

/*package whatever //do not write package name here */
 
import java.io.*;
 
// A linked list node
class Node {
    int data;
    Node next;
    Node(int x)
    {
        data = x;
        next = null;
    }
}
 
// A linked list class
class LinkedList {
 
    // head and tail pointer of Node
    Node head = null;
    Node tail = null;
 
    // Non-parameterized constructor
    LinkedList() { head = tail = null; }
 
    // Copy constructor to copy the data
    // members of one list into another
    LinkedList(LinkedList list)
    {
        if (list.head == null) {
            head = tail = null;
            return;
        }
 
        // Make a Node pointer temp and
        // initialize it to the head of list
        Node temp = list.head;
 
        // This loop is creating the new
        // linked list by copying the
        // data of list
        while (temp != null) {
            Node newNode = new Node(temp.data);
 
            if (head == null) {
                head = newNode;
                tail = newNode;
            }
            else {
                tail.next = newNode;
                tail = newNode;
            }
            temp = temp.next;
        }
    }
 
    // This function insert create a node
    // with given value and inserts the
    // node at the end of linked list
    void insert(int x)
    {
        // Allocate the temp Node and
        // put x as data into it
        Node temp = new Node(x);
 
        // Check if the head is NULL
        if (head == null) {
            head = temp;
            return;
        }
        else {
            Node t = head;
            while (t.next != null) {
                t = t.next;
            }
            t.next = temp;
        }
    }
 
    // This function prints contents of
    // linked list starting from head
    void print()
    {
        if (head == null) {
            System.out.println("List is empty");
            return;
        }
        Node temp = head;
        while (temp != null) {
            System.out.print(temp.data + " ");
            temp = temp.next;
        }
        System.out.println();
    }
}
 
class GFG {
    public static void main(String[] args)
    {
        // Creating object l1 of linked list
        LinkedList l1 = new LinkedList();
 
        l1.insert(1);
        l1.insert(9);
        l1.insert(5);
        l1.insert(7);
 
        System.out.print("Linked list l1 are: ");
        l1.print();
 
        // Copying l1 into l2
        LinkedList l2 = new LinkedList(l1);
        System.out.print("Linked list l2 are: ");
        l2.print();
    }
}

C#

// A complete working C# program to
// initialize linked list with Copy
// constructor
using System;
 
// A linked list node
class Node {
  public int data;
  public Node next;
  public Node(int x)
  {
    data = x;
    next = null;
  }
}
 
// A linked list class
class LinkedList {
 
  // head and tail pointer of Node
  public Node head = null;
  public Node tail = null;
 
  // Non-parameterized constructor
  public LinkedList() { head = tail = null; }
 
  // Copy constructor to copy the data
  // members of one list into another
  public LinkedList(LinkedList list)
  {
    if (list.head == null) {
      head = tail = null;
      return;
    }
 
    // Make a Node pointer temp and
    // initialize it to the head of list
    Node temp = list.head;
 
    // This loop is creating the new
    // linked list by copying the
    // data of list
    while (temp != null) {
      Node newNode = new Node(temp.data);
 
      if (head == null) {
        head = newNode;
        tail = newNode;
      }
      else {
        tail.next = newNode;
        tail = newNode;
      }
      temp = temp.next;
    }
  }
 
  // This function insert create a node
  // with given value and inserts the
  // node at the end of linked list
  public void insert(int x)
  {
    // Allocate the temp Node and
    // put x as data into it
    Node temp = new Node(x);
 
    // Check if the head is NULL
    if (head == null) {
      head = temp;
      return;
    }
    else {
      Node t = head;
      while (t.next != null) {
        t = t.next;
      }
      t.next = temp;
    }
  }
 
  // This function prints contents of
  // linked list starting from head
  public void print()
  {
    if (head == null) {
      Console.WriteLine("List is empty");
      return;
    }
    Node temp = head;
    while (temp != null) {
      Console.Write(temp.data + " ");
      temp = temp.next;
    }
    Console.WriteLine();
  }
}
 
public class GFG {
 
  static public void Main()
  {
 
    // Code
    // Creating object l1 of linked list
    LinkedList l1 = new LinkedList();
 
    l1.insert(1);
    l1.insert(9);
    l1.insert(5);
    l1.insert(7);
 
    Console.Write("Linked list l1 are: ");
    l1.print();
 
    // Copying l1 into l2
    LinkedList l2 = new LinkedList(l1);
    Console.Write("Linked list l2 are: ");
    l2.print();
  }
}
 
// This code is contributed by lokeshmvs21.

Javascript

class Node {
    constructor(data) {
        this.data = data;
        this.next = null;
    }
}
 
class LinkedList {
    constructor() {
        this.head = null;
        this.tail = null;
    }
 
    insert(x) {
        let temp = new Node(x);
 
        if (this.head === null) {
            this.head = temp;
            return;
        }
        else {
            let t = this.head;
            while (t.next !== null) {
                t = t.next;
            }
            t.next = temp;
        }
    }
 
    print() {
        if (this.head === null) {
            console.log("List is empty");
            return;
        }
        let temp = this.head;
        while (temp !== null) {
            console.log(temp.data);
            temp = temp.next;
        }
    }
}
 
// Driver code
let l1 = new LinkedList();
l1.insert(1);
l1.insert(9);
l1.insert(5);
l1.insert(7);
console.log("linked list l1 are: ");
l1.print();
 
let l2 = new LinkedList();
l2.head = l1.head; //copying the list
console.log("linked list l2 are: ");
l2.print();

Python3

# A linked list node
class Node:
    def __init__(self, x):
        self.data = x
        self.next = None
 
# A linked list class
class LinkedList:
    def __init__(self, lst=None):
        self.head = None
        self.tail = None
        if lst:
            temp = lst.head
            while temp:
                new_node = Node(temp.data)
                if not self.head:
                    self.head = new_node
                    self.tail = new_node
                else:
                    self.tail.next = new_node
                    self.tail = new_node
                temp = temp.next
     
    # This function insert create a node
    # with given value and inserts the
    # node at the end of linked list
    def insert(self, x):
        # Allocate the temp Node and
        # put x as data into it
        temp = Node(x)
 
        # Check if the head is NULL
        if not self.head:
            self.head = temp
            return
        else:
            t = self.head
            while t.next:
                t = t.next
            t.next = temp
     
    # This function prints contents of
    # linked list starting from head
    def print(self):
        if not self.head:
            print("List is empty")
            return
        temp = self.head
        while temp:
            print(temp.data, end=" ")
            temp = temp.next
        print()
 
# Driver code
if __name__ == '__main__':
    # Creating object l1 of linked list
    l1 = LinkedList()
    l1.insert(1)
    l1.insert(9)
    l1.insert(5)
    l1.insert(7)
    print("Linked list l1 are: ", end="")
    l1.print()
 
    # Copying l1 into l2
    l2 = LinkedList(l1)
    print("Linked list l2 are: ", end="")
    l2.print()

Output

linked list l1 are: 1 9 5 7 
linked list l2 are: 1 9 5 7

Copy Constructor and Linked List

C++

Java

C#

Javascript

Python3

Different methods to initialize a Linked List

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Copy Constructor and Linked List

C++

Java

C#

Javascript

Python3

Different methods to initialize a Linked List

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Categories

Contact US