Java Program To Merge A Linked List Into Another Linked List At Alternate Positions
Last Updated :
14 Dec, 2022
Given two linked lists, insert nodes of the second list into the first list at alternate positions of the first list.
For example, if first list is 5->7->17->13->11 and second is 12->10->2->4->6, the first list should become 5->12->7->10->17->2->13->4->11->6 and second list should become empty. The nodes of the second list should only be inserted when there are positions available. For example, if the first list is 1->2->3 and the second list is 4->5->6->7->8, then the first list should become 1->4->2->5->3->6 and the second list to 7->8.
Use of extra space is not allowed (Not allowed to create additional nodes), i.e., insertion must be done in-place. The expected time complexity is O(n) where n is the number of nodes in the first list.
The idea is to run a loop while there are available positions in first loop and insert nodes of second list by changing pointers. Following are implementations of this approach.
Java
public class LinkedList
{
Node head;
class Node
{
int data;
Node next;
Node(int d)
{
data = d;
next = null;
}
}
void push(int new_data)
{
Node new_node = new Node(new_data);
new_node.next = head;
head = new_node;
}
void merge(LinkedList q)
{
Node p_curr = head,
q_curr = q.head;
Node p_next, q_next;
while (p_curr != null &&
q_curr != null)
{
p_next = p_curr.next;
q_next = q_curr.next;
q_curr.next = p_next;
p_curr.next = q_curr;
p_curr = p_next;
q_curr = q_next;
}
q.head = q_curr;
}
void printList()
{
Node temp = head;
while (temp != null)
{
System.out.print(temp.data + " ");
temp = temp.next;
}
System.out.println();
}
public static void main(String args[])
{
LinkedList llist1 =
new LinkedList();
LinkedList llist2 =
new LinkedList();
llist1.push(3);
llist1.push(2);
llist1.push(1);
System.out.println(
"First Linked List:");
llist1.printList();
llist2.push(8);
llist2.push(7);
llist2.push(6);
llist2.push(5);
llist2.push(4);
System.out.println(
"Second Linked List:");
llist1.merge(llist2);
System.out.println(
"Modified first linked list:");
llist1.printList();
System.out.println(
"Modified second linked list:");
llist2.printList();
}
}
|
Output
First Linked List:
1 2 3
Second Linked List:
Modified first linked list:
1 4 2 5 3 6
Modified second linked list:
7 8
Time Complexity: O(N)
Auxiliary Space: O(1)
Please refer complete article on Merge linked list into another linked list at alternate positions for more details!
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