Find extra node in the second Linked list

Last Updated : 15 Nov, 2022

Given two Linked list L1 and L2. The second list L2 contains all the nodes of L1 along with 1 extra node. The task is to find that extra node.
Examples:

Input: L1 = 17 -> 7 -> 6 -> 16
L2 = 17 -> 7 -> 6 -> 16 -> 15
Output: 15
Explanation:
Element 15 is not present in the L1 list
Input: L1 = 10 -> 15 -> 5
L2 = 10 -> 100 -> 15 -> 5
Output: 100

Naive approach:

Run nested loops and find the nodes in L2 which is not present in L1.
The time complexity of this approach will be O(N²) where N is the length of the linked list.

Efficient approach:

If all the nodes of the L1 and L2 are XORed together then every node of A[] will give 0 with its occurrence in L2 and the extra element say X when XORed with 0 will give (X XOR 0) = X which is the result.

Below is the implementation of the above approach:

C++

// C++ program to find the  // extra node #include <bits/stdc++.h>  using namespace std;  // Node of the singly linked  // list struct Node {     int data;     Node* next; };  // Function to insert a node at  // the beginning of the singly // Linked List void push(Node** head_ref,           int new_data) {     // allocate node     Node* new_node =      (Node*)malloc(sizeof                   (struct Node));      // put in the data     new_node->data = new_data;      // link the old list of the     // new node     new_node->next = (*head_ref);      // move the head to point to      // the new node     (*head_ref) = new_node; }  int print(Node* head_ref,           Node* head_ref1) {     int ans = 0;      Node* ptr1 = head_ref;     Node* ptr2 = head_ref1;     // Traverse the linked list     while (ptr1 != NULL) {         ans ^= ptr1->data;         ptr1 = ptr1->next;     }     while (ptr2 != NULL) {         ans ^= ptr2->data;         ptr2 = ptr2->next;     }     return ans; }  // Driver program int main() {     // start with the empty list     Node* head1 = NULL;     Node* head2 = NULL;     // create the linked list     // 15 -> 16 -> 7 -> 6 -> 17     push(&head1, 17);     push(&head1, 7);     push(&head1, 6);     push(&head1, 16);      // second  LL     push(&head2, 17);     push(&head2, 7);     push(&head2, 6);     push(&head2, 16);     push(&head1, 15);     int k = print(head1, head2);     cout << k;     return 0; }

Java

// Java program to find the  // extra node class GFG {     // Node of the singly     // linked list     static class Node {         int data;         Node next;     };      // Function to insert a node at      // the beginning of the singly     // Linked List     static Node push(Node head_ref,                      int new_data)     {         // allocate node         Node new_node = new Node();          // put in the data         new_node.data = new_data;          // link the old list off         // the new node         new_node.next = (head_ref);          // move the head to point         // to the new node         (head_ref) = new_node;         return head_ref;     }      static void extra(Node head_ref1,                        Node head_ref2)     {         int ans = 0;          Node ptr1 = head_ref1;         Node ptr2 = head_ref2;          // Traverse the linked list         while (ptr1 != null) {             ans ^= ptr1.data;             ptr1 = ptr1.next;         }         while (ptr2 != null) {             ans ^= ptr2.data;             ptr2 = ptr2.next;         }          System.out.println(ans);     }      // Driver code     public static void main(String args[])     {         // start with the empty list         Node head1 = null;         Node head2 = null;         // create the linked list         // 15 . 16 . 7 . 6 . 17         head1 = push(head1, 17);         head1 = push(head1, 7);         head1 = push(head1, 6);         head1 = push(head1, 16);         head1 = push(head1, 15);                  // second LL         head2 = push(head2, 17);         head2 = push(head2, 7);         head2 = push(head2, 6);         head2 = push(head2, 16);          extra(head1, head2);     } }

Python3

# Python3 program to find the  # extra node class Node:              def __init__(self, data):           self.data = data           self.next = next            # Function to insert a node at    # the beginning of the singly  # Linked List   def push( head_ref, new_data) :         # allocate node       new_node = Node(0)          # put in the data       new_node.data = new_data          # link the old list off      # the new node       new_node.next = (head_ref)          # move the head to point     # to the new node       (head_ref) = new_node      return head_ref      def extra(head_ref1, head_ref2) :         ans = 0        ptr1 = head_ref1       ptr2 = head_ref2     # Traverse the linked list       while (ptr1 != None):         # if current node is prime,           # Find sum and product           ans ^= ptr1.data         ptr1 = ptr1.next     while(ptr2 != None):         ans^= ptr2.data         ptr2 = ptr2.next     print(ans)      ## print( "Product = ", prod)      # Driver code      # start with the empty list   head1 = None head2 = None  # create the linked list   # 15 . 16 . 7 . 6 . 17   head1 = push(head1, 17)   head1 = push(head1, 7)   head1 = push(head1, 6)   head1 = push(head1, 16)   head1 = push(head1, 15)    # create the linked list  head2 = push(head2, 17)   head2 = push(head2, 7)   head2 = push(head2, 6)   head2 = push(head2, 16)       extra(head1, head2)

// C# program to find the extra node using System;  class GFG{      // Node of the singly // linked list class Node {     public int data;     public Node next; };  // Function to insert a node at  // the beginning of the singly // Linked List static Node push(Node head_ref,                  int new_data) {          // Allocate node     Node new_node = new Node();      // Put in the data     new_node.data = new_data;      // Link the old list off     // the new node     new_node.next = (head_ref);      // Move the head to point     // to the new node     (head_ref) = new_node;          return head_ref; }  static void extra(Node head_ref1,                    Node head_ref2) {     int ans = 0;      Node ptr1 = head_ref1;     Node ptr2 = head_ref2;      // Traverse the linked list     while (ptr1 != null)     {         ans ^= ptr1.data;         ptr1 = ptr1.next;     }     while (ptr2 != null)      {         ans ^= ptr2.data;         ptr2 = ptr2.next;     }     Console.WriteLine(ans); }  // Driver code public static void Main(String []args) {          // Start with the empty list     Node head1 = null;     Node head2 = null;          // Create the linked list     // 15 . 16 . 7 . 6 . 17     head1 = push(head1, 17);     head1 = push(head1, 7);     head1 = push(head1, 6);     head1 = push(head1, 16);     head1 = push(head1, 15);              // Second LL     head2 = push(head2, 17);     head2 = push(head2, 7);     head2 = push(head2, 6);     head2 = push(head2, 16);      extra(head1, head2); } }  // This code is contributed by Rajput-Ji

JavaScript

<script>  // Javascript program to find the  // extra node  // Node of the singly linked  // list class Node {      constructor()     {         this.data = 0;         this.next = null;     } };  // Function to insert a node at  // the beginning of the singly // Linked List function push(head_ref, new_data) {     // allocate node     var new_node = new Node();      // put in the data     new_node.data = new_data;      // link the old list of the     // new node     new_node.next = (head_ref);      // move the head to point to      // the new node     (head_ref) = new_node;     return head_ref; }  function print(head_ref, head_ref1) {     var ans = 0;      var ptr1 = head_ref;     var ptr2 = head_ref1;     // Traverse the linked list     while (ptr1 != null) {         ans ^= ptr1.data;         ptr1 = ptr1.next;     }     while (ptr2 != null) {         ans ^= ptr2.data;         ptr2 = ptr2.next;     }     return ans; }  // Driver program // start with the empty list var head1 = null; var head2 = null;  // create the linked list // 15 . 16 . 7 . 6 . 17 head1 = push(head1, 17); head1 = push(head1, 7); head1 = push(head1, 6); head1 = push(head1, 16);  // second  LL head2 = push(head2, 17); head2 = push(head2, 7); head2 = push(head2, 6); head2 = push(head2, 16); head1 = push(head1, 15); var k = print(head1, head2); document.write( k);  // This code is contributed by noob2000. </script>

Output:

Time Complexity: O(N)
Space Complexity: O(1)

Find extra node in the second Linked list

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Find extra node in the second Linked list

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