Update middle_element_of_linked_list.py

data_structures/linked_list/middle_element_of_linked_list.py

@@ -2,67 +2,79 @@
 
 
 class Node:
+    """Represents a node in the linked list."""
+
     def __init__(self, data: int) -> None:
         self.data = data
         self.next = None
 
 
 class LinkedList:
-    def __init__(self):
+    """Represents a linked list."""
+
+    def __init__(self) -> None:
         self.head = None
+        self.size = 0  # Keep track of the list size
 
-    def push(self, new_data: int) -> int:
+    def push(self, new_data: int) -> None:
+        """Adds a new node to the front of the list."""
         new_node = Node(new_data)
         new_node.next = self.head
         self.head = new_node
-        return self.head.data
+        self.size += 1  # Increment the list size
 
     def middle_element(self) -> int | None:
-        """
-        >>> link = LinkedList()
-        >>> link.middle_element()
-        No element found.
-        >>> link.push(5)
-        5
-        >>> link.push(6)
-        6
-        >>> link.push(8)
-        8
-        >>> link.push(8)
-        8
-        >>> link.push(10)
-        10
-        >>> link.push(12)
-        12
-        >>> link.push(17)
-        17
-        >>> link.push(7)
-        7
-        >>> link.push(3)
-        3
-        >>> link.push(20)
-        20
-        >>> link.push(-20)
-        -20
-        >>> link.middle_element()
-        12
-        >>>
-        """
-        slow_pointer = self.head
-        fast_pointer = self.head
-        if self.head:
-            while fast_pointer and fast_pointer.next:
-                fast_pointer = fast_pointer.next.next
-                slow_pointer = slow_pointer.next
-            return slow_pointer.data
-        else:
+        """Returns the middle element of the list."""
+        if not self.head:
             print("No element found.")
             return None
 
+        slow_pointer = self.head
+        fast_pointer = self.head
+        while fast_pointer and fast_pointer.next:
+            fast_pointer = fast_pointer.next.next
+            slow_pointer = slow_pointer.next
+        return slow_pointer.data
+
+    def __str__(self) -> str:
+        """Returns a string representation of the list."""
+        nodes = []
+        current = self.head
+        while current:
+            nodes.append(str(current.data))
+            current = current.next
+        return " -> ".join(nodes)
+
+
+def find_middle_element(linked_list: LinkedList) -> int | None:
+    """
+    Algorithm: Find the Middle Element of a Linked List
+
+    This algorithm uses the slow and fast pointer technique to find the middle element of a linked list.
+
+    Time Complexity: O(n/2) = O(n)
+    Space Complexity: O(1)
+
+    :param linked_list: The linked list to find the middle element of
+    :return: The middle element of the linked list, or None if the list is empty
+    """
+    if not linked_list.head:
+        print("No element found.")
+        return None
+
+    slow_pointer = linked_list.head
+    fast_pointer = linked_list.head
+    while fast_pointer and fast_pointer.next:
+        fast_pointer = fast_pointer.next.next
+        slow_pointer = slow_pointer.next
+    return slow_pointer.data
+
 
 if __name__ == "__main__":
     link = LinkedList()
-    for _ in range(int(input().strip())):
-        data = int(input().strip())
+    num_elements = int(input("Enter the number of elements: "))
+    for _ in range(num_elements):
+        data = int(input("Enter element {}: ".format(_ + 1)))
         link.push(data)
-    print(link.middle_element())
+    print("Linked List:", link)
+    print("Middle Element:", find_middle_element(link))