Discover data structures and algorithms using Python. Gain insights into solving real-world problems and typical interview questions with detailed reviews, explanations, and hands-on coding exercises.

Data structures and algorithms are among the most fundamental concepts of Computer Science. Whether it’s real-world problems you’re trying to solve or the typical coding question asked in an interview, almost every problem requires you to demonstrate a deep understanding of data structures and algorithms. 

This course is a detailed review of some of the most common data structures and algorithms that you’ll see in interviews and your everyday work. With implementation details, thorough explanations, and hands-on coding exercises, you’ll quickly gain the confidence you need to solve any problem, no matter the situation.

Data Structures and Algorithms in Python

In this lesson, we investigate how to determine whether a given linked list is either a singly linked list or a circular linked list. 

## Implementation

Have a look at the coding solution below:

def is_circular_linked_list(self, input_list):
  if input_list.head:
    cur = input_list.head
    while cur.next:
      cur = cur.next
      if cur.next == input_list.head:
        return True
    return False
  else:
    return False

## Explanation

Let's discuss the class method `is_circular_linked_list`. First, we check whether or not parameter is empty. If yes, we simply return `False`. Otherwise, we proceed as follows:

On **line 3**, we initialize `cur` to `input_list.head` so that we are able to traverse `input_list` that has been passed to `is_circular_linked_list`. On **line 4** we set up a `while` loop which runs until `cur.next` becomes `None`. If `cur.next` becomes `None`, it implies that `input_list` must not be a circular linked list and therefore, if the `while` loop terminates, we return `False` on **line 8**. On the other hand, we update `cur` to `cur.next` in the `while` loop on **line 5**, and if we reach a node while traversing such that the next node is the head node, then this confirms that `input_list` is indeed a `circular_linked_list`. Hence, if the condition on **line 6** turns out to be `True`, we return `True` from the method on **line 7**.

As you can see, the `is_circular_linked_list` method was pretty straightforward. Below we test it on a singly linked list and on a circular linked list:

In this lesson, we investigate how to determine whether a given linked list is either a singly linked list or a circular linked list. 

# Implementation

Have a look at the coding solution below:

# Explanation

Let's discuss the class method `is_circular_linked_list`. First, we check whether or not parameter is empty. If yes, we simply return `False`. Otherwise, we proceed as follows:

On **line 3**, we initialize `cur` to `input_list.head` so that we are able to traverse `input_list` that has been passed to `is_circular_linked_list`. On **line 4** we set up a `while` loop which runs until `cur.next` becomes `None`. If `cur.next` becomes `None`, it implies that `input_list` must not be a circular linked list and therefore, if the `while` loop terminates, we return `False` on **line 8**. On the other hand, we update `cur` to `cur.next` in the `while` loop on **line 5**, and if we reach a node while traversing such that the next node is the head node, then this confirms that `input_list` is indeed a `circular_linked_list`. Hence, if the condition on **line 6** turns out to be `True`, we return `True` from the method on **line 7**.

As you can see, the `is_circular_linked_list` method was pretty straightforward. Below we test it on a singly linked list and on a circular linked list:

This lesson contains the solution review for the challenge of determining whether a given linked list is circular or not. 

Introduction

Stack

Singly Linked Lists

Circular Linked Lists

Doubly Linked Lists

Arrays

Binary Trees

Binary Search Trees

Binary Search

Recursion

String Processing

Solution Review: Is Circular Linked List

Implementation

Explanation