Adds operations for circular linked list

data_structures/linked_list/circular_linked_list.py

@@ -0,0 +1,224 @@
+import typing
+
+
+class Node:
+    """
+    Class to represent a single node.
+
+    Each node has following attributes
+    * data
+    * next_ptr
+    """
+
+    def __init__(self, data: typing.Any):
+        self.data = data
+        self.next_ptr = None
+
+    def set_data(self, value: typing.Any):
+        """
+        Set the data field of the node to given value.
+        >>> node = Node(1)
+        >>> node.set_data(2)
+        >>> node.get_data()
+        2
+        """
+        self.data = value
+
+    def get_data(self) -> typing.Any:
+        """
+        Returns the data field of the current node.
+        >>> node = Node(1)
+        >>> node.get_data()
+        1
+        """
+        return self.data
+
+    def set_next(self, value: typing.Type['Node']):
+        """
+        Sets the next pointer of the current node.
+        >>> node, node1 = Node(1), Node(2)
+        >>> node.set_next(node1)
+        >>> node.get_next().get_data()
+        2
+        """
+        self.next_ptr = value
+
+    def get_next(self) -> typing.Type['Node']:
+        """
+        Returns the next pointer of the current node.
+        >>> node = Node(1)
+        >>> node.get_next() is None
+        True
+        """
+        return self.next_ptr
+
+    def has_next(self) -> bool:
+        """
+        Checks if the current node has a valid next node.
+        >>> node = Node(1)
+        >>> node.has_next()
+        False
+        """
+        return self.next_ptr is not None
+
+
+class CircularLinkedList:
+    """
+    Class to represent the CircularLinkedList.
+
+    CircularLinkedList has following attributes.
+    * HEAD
+    * length
+    """
+
+    def __init__(self):
+        self.head = None
+        self.length = 0
+
+    def __len__(self) -> int:
+        """
+        Dunder method to return length of the CircularLinkedList
+        >>> cll = CircularLinkedList()
+        >>> len(cll)
+        0
+        >>> cll.append(1)
+        >>> len(cll)
+        1
+        """
+        return self.length
+
+    def __str__(self) -> str:
+        """
+        Dunder method to represent the string representation of the CircularLinkedList
+        >>> cll = CircularLinkedList()
+        >>> print(cll)
+        Empty linked list
+        >>> cll.append(1)
+        >>> cll.append(2)
+        >>> print(cll)
+        <Node data=1> => <Node data=2>
+        """
+        current_node = self.head
+        if not current_node:
+            return "Empty linked list"
+
+        result = [f"<Node data={current_node.get_data()}>"]
+        current_node = current_node.get_next()
+
+        while current_node != self.head:
+            result.append(f"<Node data={current_node.get_data()}>")
+            current_node = current_node.get_next()
+
+        return " => ".join(result)
+
+    def append(self, data: typing.Any):
+        """
+        Adds a node with given data to the end of the CircularLinkedList
+        >>> cll = CircularLinkedList()
+        >>> cll.append(1)
+        >>> cll.append(2)
+        >>> len(cll)
+        2
+        >>> print(cll)
+        <Node data=1> => <Node data=2>
+        """
+        current_node = self.head
+
+        new_node = Node(data)
+        new_node.set_next(new_node)
+
+        if current_node is None:
+            self.head = new_node
+        else:
+            while current_node.get_next() != self.head:
+                current_node = current_node.get_next()
+
+            current_node.set_next(new_node)
+            new_node.set_next(self.head)
+
+        self.length += 1
+
+    def prepend(self, data: typing.Any):
+        """
+        Adds a ndoe with given data to the front of the CircularLinkedList
+        >>> cll = CircularLinkedList()
+        >>> cll.prepend(1)
+        >>> cll.prepend(2)
+        >>> len(cll)
+        2
+        >>> print(cll)
+        <Node data=2> => <Node data=1>
+        """
+        current_node = self.head
+
+        new_node = Node(data)
+        new_node.set_next(new_node)
+
+        if current_node is None:
+            self.head = new_node
+        else:
+            while current_node.get_next() != self.head:
+                current_node = current_node.get_next()
+
+            current_node.set_next(new_node)
+            new_node.set_next(self.head)
+
+            self.head = new_node
+
+        self.length += 1
+
+    def delete_front(self):
+        """
+        Removes the 1st node from the CircularLinkedList
+        >>> cll = CircularLinkedList()
+        >>> cll.append(1)
+        >>> cll.append(2)
+        >>> print(cll)
+        <Node data=1> => <Node data=2>
+        >>> cll.delete_front()
+        >>> print(cll)
+        <Node data=2>
+        """
+        if self.head is None:
+            raise IndexError()
+
+        current_node = self.head
+
+        if current_node.get_next() == current_node:
+            self.head, self.length = None, 0
+        else:
+            while current_node.get_next() != self.head:
+                current_node = current_node.get_next()
+
+            current_node.set_next(self.head.get_next())
+            self.head = self.head.get_next()
+
+        self.length -= 1
+
+    def delete_rear(self):
+        """
+        Removes the last node from the CircularLinkedList
+        >>> cll = CircularLinkedList()
+        >>> cll.append(1)
+        >>> cll.append(2)
+        >>> print(cll)
+        <Node data=1> => <Node data=2>
+        >>> cll.delete_rear()
+        >>> print(cll)
+        <Node data=1>
+        """
+        if self.head is None:
+            raise IndexError()
+
+        temp_node, current_node = self.head, self.head
+
+        if current_node.get_next() == current_node:
+            self.head, self.length = None, 0
+        else:
+            while current_node.get_next() != self.head:
+                temp_node = current_node
+                current_node = current_node.get_next()
+
+            temp_node.set_next(current_node.get_next())
+
+        self.length -= 1