Java: Remove duplicates from a sorted linked list

Last update on April 01 2025 10:50:37 (UTC/GMT +8 hours)

Remove Duplicates in Linked List

Write a Java program to remove duplicates from a sorted linked list.

Pictorial Presentation:

Sample Solution:

Java Code:

class LinkedList {
	Node head; // Reference to the head node of the linked list

	/* Linked list Node */
	class Node {
		int data; // Data stored in the node
		Node next; // Reference to the next node

		Node(int d) {
			data = d;
			next = null;
		}
	}

	// Method to remove duplicate elements from the linked list
	void remove_Duplicates() {
		Node current = head; // Initialize the current node to the head
		Node next_next; // Reference to the next of the next node

		if (head == null)
			return; // If the linked list is empty, return

		while (current.next != null) {
			if (current.data == current.next.data) {
				next_next = current.next.next;
				current.next = null; // Remove the duplicate node
				current.next = next_next; // Update the next reference
			} else
				current = current.next; // Move to the next node
		}
	}

	// Method to insert a new node at the front of the linked list
	public void push(int new_data) {
		Node new_node = new Node(new_data); // Create a new node
		new_node.next = head; // Set the next of the new node to the current head
		head = new_node; // Update the head to the new node
	}

	// Method to print the linked list
	void printList() {
		Node temp = head; // Initialize a temporary node with the head
		while (temp != null) {
			System.out.print(temp.data); // Print the data of the current node
			if (temp.next != null) {
				System.out.print("->"); // Print an arrow to indicate the next node
			}
			temp = temp.next; // Move to the next node
		}
		System.out.println(); // Print a new line to complete the list
	}

	// Driver program to test the above functions
	public static void main(String args[]) {
		LinkedList l_list = new LinkedList();
		
		// Insert data into the linked list
		l_list.push(17);
		l_list.push(17);
		l_list.push(16);
		l_list.push(15);
		l_list.push(15);
		l_list.push(14);
		l_list.push(13);
		l_list.push(12);
		l_list.push(12);
		
		System.out.println("Original List with duplicate elements:");
		l_list.printList();
		
		l_list.remove_Duplicates(); // Remove duplicates
		
		System.out.println("After removing duplicates from the said list:");
		l_list.printList();
	}
}

Sample Output:

Original List with duplicate elements:
12->12->13->14->15->15->16->17->17
After removing duplicates from the said list:
12->13->14->15->16->17

Flowchart:

For more Practice: Solve these Related Problems:

• Modify the program to remove duplicates from an unsorted linked list.
• Write a program to remove duplicates from a doubly linked list.
• Modify the program to return the length of the new linked list.
• Write a program to remove duplicates in a circular linked list.

Java Code Editor:

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