Delete_duplicate-value_nodes.py

"""
Delete duplicate-value nodes from a sorted linked list
-------------------------------------------
Link: https://www.hackerrank.com/contests/wissen-coding-challenge-2021/challenges/delete-duplicate-value-nodes-from-a-sorted-linked-list
-------------------------------------------

You are given the pointer to the head node of a sorted linked list, where the data in the nodes is in ascending order. Delete nodes and return a sorted list with each distinct value in the original list. The given head pointer may be null indicating that the list is empty.

Example

head refers to the first node in the list 1 -> 2 -> 2 -> 3 -> 3 -> 3 -> 3 -> NULL.

Remove 1 of the 2 data values and return head pointing to the revised list 1 -> 2 -> 3 -> NULL.

Function Description

Complete the removeDuplicates function in the editor below.

removeDuplicates has the following parameter:

SinglyLinkedListNode pointer head: a reference to the head of the list

Returns:
SinglyLinkedListNode pointer: a reference to the head of the revised list

Input Format:
The first line contains an integer t, the number of test cases.

The format for each test case is as follows:

The first line contains an integer n, the number of elements in the linked list.
Each of the next n lines contains an integer, the data value for each of the elements of the linked list.

Sample Input

STDIN   Function
-----   --------
1       t = 1
5       n = 5
1       data values = 1, 2, 2, 3, 4
2
2
3
4

Sample Output:
1 2 3 4 

Explanation:
The initial linked list is: 1 -> 2 -> 2 -> 3 -> 4 -> NULL.

The final linked list is: 1 -> 2 -> 3 -> 4 -> NULL.

"""

(Python Solution)
def removeDuplicates(head):
    node = head
    next = head.next
    while next:
        if node.data != next.data:
            node = node.next
        next = next.next
        node.next = next
    return head
	
(Scala Solution)
def removeDuplicates(head: SinglyLinkedListNode): SinglyLinkedListNode = {
	var current = head
	var last: SinglyLinkedListNode = null
	while (current != null) {
		if (last == null || last.data != current.data) {
			last = current;
		} else {
			last.next = current.next;
		}
		current = current.next
	}
	head
}