added algorithm to remove duplicates from a linked list

data_structures/linked_list/remove_duplicates.py

@@ -0,0 +1,109 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass
+class Node:
+    data: int
+    next_node: Node | None = None
+
+
+def print_linked_list(head: Node | None) -> None:
+    """
+    Print the entire linked list iteratively.
+
+    >>> head = insert_node(None, 0)
+    >>> head = insert_node(head, 2)
+    >>> head = insert_node(head, 1)
+    >>> print_linked_list(head)
+    0->2->1
+    >>> head = insert_node(head, 4)
+    >>> head = insert_node(head, 5)
+    >>> print_linked_list(head)
+    0->2->1->4->5
+    """
+    if head is None:
+        return
+    while head.next_node is not None:
+        print(head.data, end="->")
+        head = head.next_node
+    print(head.data)
+
+
+def insert_node(head: Node | None, data: int) -> Node | None:
+    """
+    Insert a new node at the end of a linked list
+    and return the new head.
+
+    >>> head = insert_node(None, 10)
+    >>> head = insert_node(head, 9)
+    >>> head = insert_node(head, 8)
+    >>> print_linked_list(head)
+    10->9->8
+    """
+    new_node = Node(data)
+    if head is None:
+        return new_node
+
+    temp_node = head
+    while temp_node.next_node:
+        temp_node = temp_node.next_node
+    temp_node.next_node = new_node
+    return head
+
+
+def remove_duplicates(head: Node | None) -> Node | None:
+    """
+    Remove nodes with duplicate data
+
+    >>> head=insert_node(None,1)
+    >>> head=insert_node(head,1)
+    >>> head=insert_node(head,2)
+    >>> head=insert_node(head,3)
+    >>> head=insert_node(head,3)
+    >>> head=insert_node(head,4)
+    >>> head=insert_node(head,5)
+    >>> head=insert_node(head,5)
+    >>> head=insert_node(head,5)
+    >>> new_head= remove_duplicates(head)
+    >>> print_linked_list(new_head)
+    1->2->3->4->5
+    """
+    if head is None or head.next_node is None:
+        return head
+
+    has_occurred = {}
+
+    new_head = head
+    last_node = head
+    has_occurred[head.data] = True
+    current_node = None
+    if head.next_node:
+        current_node = head.next_node
+    while current_node is not None:
+        if current_node.data not in has_occurred:
+            last_node.next_node = current_node
+            last_node = current_node
+            has_occurred[current_node.data] = True
+        current_node = current_node.next_node
+    last_node.next_node = None
+    return new_head
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
+    head = insert_node(None, 1)
+    head = insert_node(head, 1)
+    head = insert_node(head, 2)
+    head = insert_node(head, 3)
+    head = insert_node(head, 3)
+    head = insert_node(head, 4)
+    head = insert_node(head, 5)
+    head = insert_node(head, 5)
+
+    new_head = remove_duplicates(head)
+    print_linked_list(new_head)