circular

# Python code to perform circular linked list operations

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None


class CircularLinkedList:
    def __init__(self):
        self.last = None

    def add_to_empty(self, data):

        if self.last is not None:
            return self.last

        # allocate memory to the new node and add data to the node
        new_node = Node(data)

        # assign last to new_node
        self.last = new_node

        # create link to itself
        self.last.next = self.last
        return self.last

    # add node to the front
    def add_front(self, data):

        # check if the list is empty
        if self.last is None:
            return self.add_to_empty(data)

        # allocate memory to the new node and add data to the node
        new_node = Node(data)

        # store the address of the current first node in the new_node
        new_node.next = self.last.next

        # make new_node as last
        self.last.next = new_node

        return self.last

    # add node to the end
    def add_end(self, data):
        # check if the node is empty
        if self.last is None:
            return self.add_to_empty(data)

        # allocate memory to the new node and add data to the node
        newNode = Node(data)

        # store the address of the last node to next of newNode
        newNode.next = self.last.next

        # point the current last node to the newNode
        self.last.next = newNode

        # make newNode as the last node
        self.last = newNode

        return self.last

    # insert node after a specific node
    def add_after(self, data, item):

        # check if the list is empty
        if self.last is None:
            return None

        new_node = Node(data)
        p = self.last.next
        while p:

            # if the item is found, place new_node after it
            if p.data == item:

                # make the next of the current node as the next of new_node
                new_node.next = p.next

                # put new_node to the next of p
                p.next = new_node

                if p == self.last:
                    self.last = new_node
                    return self.last
                else:
                    return self.last
            p = p.next
            if p == self.last.next:
                print(item, "The given node is not present in the list")
                break

    # delete a node
    def delete_node(self, last, key):

        # If linked list is empty
        if last is None:
            return

        # If the list contains only a single node
        if last.data == key and last.next == last:
            last = None

        temp = last
        d = None

        # if last node is to be deleted
        if last.data == key:

            # find the node before the last node
            while temp.next != last:
                temp = temp.next

            # point temp node to the next of last i.e. first node
            temp.next = last.next
            last = temp.next

        # travel to the node to be deleted
        while temp.next != last and temp.next.data != key:
            temp = temp.next

        # if node to be deleted was found
        if temp.next.data == key:
            d = temp.next
            temp.next = d.next

        return last

    def traverse(self):
        if self.last is None:
            print("The list is empty")
            return

        new_node = self.last.next
        while new_node:
            print(new_node.data, end=" ")
            new_node = new_node.next
            if new_node == self.last.next:
                break


if __name__ == "__main__":
    circular = CircularLinkedList()

    # add node to the circular linked list
    last = circular.add_to_empty("Glen")
    last = circular.add_end("Espe")
    last = circular.add_front("Ralph")
    last = circular.add_after("Frieda", "Ralph")

    print("The node of the circular linked list: ")
    circular.traverse()
    print()

    # delete last node of the circular linked list
    last = circular.delete_node(last, "Espe")
    print("\nThe node of the circular linked list after deletion: ")
    circular.traverse()