Merge odd and even positioned nodes of two Linked Lists alternately
Given two linked lists L1 and L2, the task is to print a new list obtained by merging odd position nodes of L1 with the even positioned nodes of L2 alternately.
Examples:
Input: L1 = 8->5->3->2->10->NULL, L2 = 11->13->1->6->9->NULL
Output: 8->13->3->6->10->NULL
Explanation:
The odd positioned nodes of L1 are {8, 3, 10} and the even positioned nodes L2 are {13, 6}.
Merging them alternately generates the linked list 8->13->3->6->10->NULLInput: L1 = 1->5->10->12->13->19->6->NULL, L2 = 2->7->9->NULL
Output: 1->7->10->13->6->NULL
Explanation:
The odd positioned nodes of L1 are {1, 10, 13, 6} and the even positioned node of L2 is {7}.
Merging them alternately generates the linked list 1->7->10->13->6->NULL
Approach: Follow the steps below to solve the problem:
- Start traversing from the first node of L1 and for the second node of L2 simultaneously.
- Add the first node of L1 to the resultant list and connect it with the second node of L2 and move to the next odd node in L1. Similarly, add connect the second node of L2 to the current odd node of L1 and move to the next even node in L2.
- Repeat the above step until the end of one of the lists is reached.
- Traverse the other list and keep adding the required nodes from that list to the resultant list.
- Finally, print the resultant list.
Below is the implementation of the above approach:
C++
// C++ program to implement// the above approach#include <bits/stdc++.h>using namespace std;// Structure of a Nodeclass node {public: int data; node* next; node(int d) { data = d; next = NULL; }};// Function to insert the node// at the head of the linkedlistvoid insert_at_head(node*& head, int data){ node* n = new node(data); n->next = head; head = n; return;}// Function to print the linked listvoid print(node* head){ while (head != NULL) { cout << head->data << " "; head = head->next; } cout << endl; return;}// Function to merge the odd and// even positioned nodes of two// given linked lists alternatelynode* merge_alternate(node* head1, node* head2){ // Traverse from the second // node of second linked list if (head2) head2 = head2->next; // Stores the head of // the resultant list node* head3 = NULL; // Stores the current node node* cur = NULL; // Store the first node of // first list in the result if (head1) head3 = head1; // Otherwise else head3 = head2; // Traverse until end of a // one of the list is reached while (head1 != NULL && head2 != NULL) { // If there is a previous node then // connect that with the current node if (cur) cur->next = head1; // Update the current node cur = head1; // If next odd node exists if (head1->next != NULL) // Store the next odd node head1 = head1->next->next; // Otherwise else // Reach end of list head1 = NULL; // Connect the first node // with the second node cur->next = head2; // Update the current node cur = head2; // If next even node exists if (head2->next != NULL) // Store the next even node head2 = head2->next->next; // Otherwise else // Reach the end of the list head2 = NULL; } // If end of the second // list has been reached while (head1 != NULL) { // Connect with the // previous node if (cur) cur->next = head1; // Update the current node cur = head1; // If next odd node exists if (head1->next != NULL) // Store the next odd node head1 = head1->next->next; // Otherwise else // Reach end of list head1 = NULL; } // If end of second list // has been reached while (head2 != NULL) { // Connect with the // previous node if (cur) cur->next = head2; // Update the current node cur = head2; // If next even node exists if (head2->next != NULL) // Store the next odd node head2 = head2->next->next; // Otherwise else // Reach end of list head2 = NULL; } // End of the resultant list if (cur) cur->next = NULL; // Returning the head of // the resultant node return head3;}// Driver Codeint main(){ node *head1 = NULL, *head2 = NULL; // Create linked list insert_at_head(head1, 6); insert_at_head(head1, 19); insert_at_head(head1, 13); insert_at_head(head1, 12); insert_at_head(head1, 10); insert_at_head(head1, 5); insert_at_head(head1, 1); insert_at_head(head2, 9); insert_at_head(head2, 7); insert_at_head(head2, 2); // Merging the linked lists head1 = merge_alternate(head1, head2); print(head1);} |
Java
// Java program to implement// the above approachimport java.util.*;class GFG{// Structure of a Nodestatic class node{ public int data; node next; node(int d) { data = d; next = null; }};// Function to insert the node// at the head of the linkedliststatic node insert_at_head(node head, int data){ node n = new node(data); n.next = head; head = n; return head;}// Function to print the linked liststatic void print(node head){ while (head != null) { System.out.print(head.data + " "); head = head.next; } System.out.println(); return;}// Function to merge the odd and// even positioned nodes of two// given linked lists alternatelystatic node merge_alternate(node head1, node head2){ // Traverse from the second // node of second linked list if (head2 != null) head2 = head2.next; // Stores the head of // the resultant list node head3 = null; // Stores the current node node cur = null; // Store the first node of // first list in the result if (head1 != null) head3 = head1; // Otherwise else head3 = head2; // Traverse until end of a // one of the list is reached while (head1 != null && head2 != null) { // If there is a previous node then // connect that with the current node if (cur != null) cur.next = head1; // Update the current node cur = head1; // If next odd node exists if (head1.next != null) // Store the next odd node head1 = head1.next.next; // Otherwise else // Reach end of list head1 = null; // Connect the first node // with the second node cur.next = head2; // Update the current node cur = head2; // If next even node exists if (head2.next != null) // Store the next even node head2 = head2.next.next; // Otherwise else // Reach the end of the list head2 = null; } // If end of the second // list has been reached while (head1 != null) { // Connect with the // previous node if (cur != null) cur.next = head1; // Update the current node cur = head1; // If next odd node exists if (head1.next != null) // Store the next odd node head1 = head1.next.next; // Otherwise else // Reach end of list head1 = null; } // If end of second list // has been reached while (head2 != null) { // Connect with the // previous node if (cur != null) cur.next = head2; // Update the current node cur = head2; // If next even node exists if (head2.next != null) // Store the next odd node head2 = head2.next.next; // Otherwise else // Reach end of list head2 = null; } // End of the resultant list if (cur != null) cur.next = null; // Returning the head of // the resultant node return head3;}// Driver Codepublic static void main(String[] args){ node head1 = null, head2 = null; // Create linked list head1 = insert_at_head(head1, 6); head1 = insert_at_head(head1, 19); head1 = insert_at_head(head1, 13); head1 = insert_at_head(head1, 12); head1 = insert_at_head(head1, 10); head1 = insert_at_head(head1, 5); head1 = insert_at_head(head1, 1); head2 = insert_at_head(head2, 9); head2 = insert_at_head(head2, 7); head2 = insert_at_head(head2, 2); // Merging the linked lists head1 = merge_alternate(head1, head2); print(head1);}}// This code is contributed by gauravrajput1 |
Python3
# Python3 program to implement# the above approach # Structure of a Nodeclass node: def __init__(self, d): self.data = d; self.next = None; # Function to insert the node# at the head of the linkedlistdef insert_at_head(head, data): n = node(data); n.next = head; head = n; return head; # Function to print the linked listdef printx(head): while (head != None): print(head.data, end = ' ') head = head.next; print() return; # Function to merge the odd and# even positioned nodes of two# given linked lists alternatelydef merge_alternate(head1, head2): # Traverse from the second # node of second linked list if (head2): head2 = head2.next; # Stores the head of # the resultant list head3 = None; # Stores the current node cur = None; # Store the first node of # first list in the result if (head1): head3 = head1; # Otherwise else: head3 = head2; # Traverse until end of a # one of the list is reached while (head1 != None and head2 != None): # If there is a previous node then # connect that with the current node if (cur): cur.next = head1; # Update the current node cur = head1; # If next odd node exists if (head1.next != None): # Store the next odd node head1 = head1.next.next; # Otherwise else: # Reach end of list head1 = None; # Connect the first node # with the second node cur.next = head2; # Update the current node cur = head2; # If next even node exists if (head2.next != None): # Store the next even node head2 = head2.next.next; # Otherwise else: # Reach the end of the list head2 = None; # If end of the second # list has been reached while (head1 != None): # Connect with the # previous node if (cur): cur.next = head1; # Update the current node cur = head1; # If next odd node exists if (head1.next != None): # Store the next odd node head1 = head1.next.next; # Otherwise else: # Reach end of list head1 = None; # If end of second list # has been reached while (head2 != None): # Connect with the # previous node if (cur): cur.next = head2; # Update the current node cur = head2; # If next even node exists if (head2.next != None): # Store the next odd node head2 = head2.next.next; # Otherwise else: # Reach end of list head2 = None; # End of the resultant list if (cur): cur.next = None; # Returning the head of # the resultant node return head3; # Driver Codeif __name__=='__main__': head1 = None head2 = None; # Create linked list head1 = insert_at_head(head1, 6); head1 = insert_at_head(head1, 19); head1 = insert_at_head(head1, 13); head1 = insert_at_head(head1, 12); head1 = insert_at_head(head1, 10); head1 = insert_at_head(head1, 5); head1 = insert_at_head(head1, 1); head2 = insert_at_head(head2, 9); head2 = insert_at_head(head2, 7); head2 = insert_at_head(head2, 2) # Merging the linked lists head1 = merge_alternate(head1, head2); printx(head1); # This code is contributed by rutvik_56 |
C#
// C# program to implement// the above approachusing System;class GFG{// Structure of a Nodeclass node{ public int data; public node next; public node(int d) { data = d; next = null; }};// Function to insert the node// at the head of the linkedliststatic node insert_at_head(node head, int data){ node n = new node(data); n.next = head; head = n; return head;}// Function to print the linked liststatic void print(node head){ while (head != null) { Console.Write(head.data + " "); head = head.next; } Console.WriteLine(); return;}// Function to merge the odd and// even positioned nodes of two// given linked lists alternatelystatic node merge_alternate(node head1, node head2){ // Traverse from the second // node of second linked list if (head2 != null) head2 = head2.next; // Stores the head of // the resultant list node head3 = null; // Stores the current node node cur = null; // Store the first node of // first list in the result if (head1 != null) head3 = head1; // Otherwise else head3 = head2; // Traverse until end of a // one of the list is reached while (head1 != null && head2 != null) { // If there is a previous // node then connect that // with the current node if (cur != null) cur.next = head1; // Update the current node cur = head1; // If next odd node exists if (head1.next != null) // Store the next odd node head1 = head1.next.next; // Otherwise else // Reach end of list head1 = null; // Connect the first node // with the second node cur.next = head2; // Update the current node cur = head2; // If next even node exists if (head2.next != null) // Store the next even node head2 = head2.next.next; // Otherwise else // Reach the end of the list head2 = null; } // If end of the second // list has been reached while (head1 != null) { // Connect with the // previous node if (cur != null) cur.next = head1; // Update the current node cur = head1; // If next odd node exists if (head1.next != null) // Store the next odd node head1 = head1.next.next; // Otherwise else // Reach end of list head1 = null; } // If end of second list // has been reached while (head2 != null) { // Connect with the // previous node if (cur != null) cur.next = head2; // Update the current node cur = head2; // If next even node exists if (head2.next != null) // Store the next odd node head2 = head2.next.next; // Otherwise else // Reach end of list head2 = null; } // End of the resultant list if (cur != null) cur.next = null; // Returning the head of // the resultant node return head3;}// Driver Codepublic static void Main(String[] args){ node head1 = null, head2 = null; // Create linked list head1 = insert_at_head(head1, 6); head1 = insert_at_head(head1, 19); head1 = insert_at_head(head1, 13); head1 = insert_at_head(head1, 12); head1 = insert_at_head(head1, 10); head1 = insert_at_head(head1, 5); head1 = insert_at_head(head1, 1); head2 = insert_at_head(head2, 9); head2 = insert_at_head(head2, 7); head2 = insert_at_head(head2, 2); // Merging the linked lists head1 = merge_alternate(head1, head2); print(head1);}}// This code is contributed by Princi Singh |
Javascript
<script>// javascript program to implement// the above approach // Structure of a Node class node { constructor(d) { this.data = d; this.next = null; } } // Function to insert the node // at the head of the linkedlist function insert_at_head( head , data) { n = new node(data); n.next = head; head = n; return head; } // Function to print the linked list function print( head) { while (head != null) { document.write(head.data + " "); head = head.next; } document.write(); return; } // Function to merge the odd and // even positioned nodes of two // given linked lists alternately function merge_alternate( head1, head2) { // Traverse from the second // node of second linked list if (head2 != null) head2 = head2.next; // Stores the head of // the resultant list head3 = null; // Stores the current node cur = null; // Store the first node of // first list in the result if (head1 != null) head3 = head1; // Otherwise else head3 = head2; // Traverse until end of a // one of the list is reached while (head1 != null && head2 != null) { // If there is a previous node then // connect that with the current node if (cur != null) cur.next = head1; // Update the current node cur = head1; // If next odd node exists if (head1.next != null) // Store the next odd node head1 = head1.next.next; // Otherwise else // Reach end of list head1 = null; // Connect the first node // with the second node cur.next = head2; // Update the current node cur = head2; // If next even node exists if (head2.next != null) // Store the next even node head2 = head2.next.next; // Otherwise else // Reach the end of the list head2 = null; } // If end of the second // list has been reached while (head1 != null) { // Connect with the // previous node if (cur != null) cur.next = head1; // Update the current node cur = head1; // If next odd node exists if (head1.next != null) // Store the next odd node head1 = head1.next.next; // Otherwise else // Reach end of list head1 = null; } // If end of second list // has been reached while (head2 != null) { // Connect with the // previous node if (cur != null) cur.next = head2; // Update the current node cur = head2; // If next even node exists if (head2.next != null) // Store the next odd node head2 = head2.next.next; // Otherwise else // Reach end of list head2 = null; } // End of the resultant list if (cur != null) cur.next = null; // Returning the head of // the resultant node return head3; } // Driver Code head1 = null, head2 = null; // Create linked list head1 = insert_at_head(head1, 6); head1 = insert_at_head(head1, 19); head1 = insert_at_head(head1, 13); head1 = insert_at_head(head1, 12); head1 = insert_at_head(head1, 10); head1 = insert_at_head(head1, 5); head1 = insert_at_head(head1, 1); head2 = insert_at_head(head2, 9); head2 = insert_at_head(head2, 7); head2 = insert_at_head(head2, 2); // Merging the linked lists head1 = merge_alternate(head1, head2); print(head1);// This code is contributed by umadevi9616</script> |
Output:
1 7 10 13 6
Time Complexity: O(N)
Auxiliary Space: O(1)
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