1603450800

# Building a Singly Linked List

Most likely you arrived at this article because your preparation for an interview has lead you down a LeetCode rabbit hole. Linked lists are a favorite of many interviewers to test an interviewees understanding of basic data structures as well as your problem solving skills. Whether you’re just a bit rusty from school or this is your first time encountering linked lists they can be a bit tricky to understand at first.

As with most problems it is helpful to start with a diagram. A linked list is a linear data structure which can be thought of as a chain, where each link in a chain is connected to the next link. In a linked list, each link in the chain will be represented as a node.

In a singly linked list, each node contains some data and then a pointer to the next node. For a doubly linked list there would also be a pointer to the previous node. The first node in the list is conventionally referred to as the head and the final node’s next pointer refers to nothing. With this diagram constructed it is now time to start coding up a singly linked list in JavaScript.

### Coding a Node Class

Since a singly linked list consists of many notes it makes sense to create a class Node that way a new node can be easily and consistently instantiated. At the instantiation of a new node the data it will contain should be know but the next node might not be known.

Figure 2: JavaScript Node Class

A doubly linked list node class would look very similar to Figure 2 but with an additional property of previous that would also initialize to null as it may not be known or it could be the head node.

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## Editing a Singly Linked List

In the previous “Data Structures in JavaScript” discussion, we walked through the methodology used to construct a node class which represent each “link” in the “chain” that is a linked list. From there we discussed how to construct a singly linked list from a an array. Building on the previous discussion, we will now dive into editing that singly linked list. If you are not familiar with the code and terminology covered in the previous article it is recommended you review Building a Singly Linked List.

With a linked list there are three ways to edit the list: update a nodes data property, add a node to the list or delete a node from the list. In all these cases, we will want to access a specific place in the singly linked list. Depending on the situation, you might want to edit the nth node from the head of the list, the nth node from the end of the list, or a node of a particular data value. For this discussion, we will assume that we are interested in editing the nth Node from the head of the list. With this in mind, we can step through a singly linked list from the head to the nth a node using a simple for loop as shown in Figure 1.

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## What Is a Linked List?

A linked list is a basic data structure. It is a collection of nodes that connects each node to the next node with a pointer.

Each node consists of two items:

• Data (such as a number)
• Pointer to the next node

Here is an illustration of a linked list

A linked list forms a chain of nodes. Each node holds data and points to the next node. Image by the author.

#programming #coding #python #how to create a linked list in python #create a linked list #linked list

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## Beyonic API Python Examples.

The beyonic APIs Docs Reference: https://apidocs.beyonic.com/

Discuss Beyonic API on slack

The Beyonic API is a representational state transfer, REST based application programming interface that lets you extend the Beyonic dashboard features into your application and systems, allowing you to build amazing payment experiences.

With the Beyonic API you can:

• Receive and send money and prepaid airtime.
• List currencies and networks supported by the Beyonic API.
• Check whether a bank is supported by the Beyonic API.
• View your account transactions history.
• Use webhooks to send notifications to URLs on your server that when specific events occur in your Beyonic account (e.g. payments).

### Getting Help

For usage, general questions, and discussions the best place to go to is Beyhive Slack Community, also feel free to clone and edit this repository to meet your project, application or system requirements.

To start using the Beyonic Python API, you need to start by downloading the Beyonic API official Python client library and setting your secret key.

Install the Beyonic API Python Official client library

>>> pip install beyonic

To set the secrete key install the python-dotenv modeule, Python-dotenv is a Python module that allows you to specify environment variables in traditional UNIX-like “.env” (dot-env) file within your Python project directory, it helps us work with SECRETS and KEYS without exposing them to the outside world, and keep them safe during development too.

Installing python-dotenv modeule

>>> pip install python-dotenv

Creating a .env file to keep our secrete keys.

>>> touch .env

Inside your .env file specify the Beyonic API Token .

.env file

BEYONIC_ACCESS_KEY = "enter your API "

You will get your API Token by clicking your user name on the bottom left of the left sidebar menu in the Beyonic web portal and selecting ‘Manage my account’ from the dropdown menu. The API Token is shown at the very bottom of the page.

#### getExamples.py

import os
import beyonic

myapi = os.environ['BEYONIC_ACCESS_KEY']

beyonic.api_key = myapi

# Listing account: Working.
accounts = beyonic.Account.list()
print(accounts)

#Listing currencies: Not working yet.
'''
supported_currencies = beyonic.Currency.list()
print(supported_currencies)

Supported currencies are: USD, UGX, KES, BXC, GHS, TZS, RWF, ZMW, MWK, BIF, EUR, XAF, GNF, XOF, XOF
'''

#Listing networks: Not working yet.
"""
networks = beyonic.Network.list()
print(networks)
"""

#Listing transactions: Working.
transactions = beyonic.Transaction.list()
print(transactions)

#Listing contact: Working.
mycontacts = beyonic.Contact.list()
print(mycontacts)

#Listing events: Not working yet.
'''
events = beyonic.Event.list()
print(events)

Error: AttributeError: module 'beyonic' has no attribute 'Event'
'''

Docker file

FROM python:3.8-slim-buster

COPY . .

COPY ./requirements.txt ./requirements.txt

WORKDIR .

RUN pip install -r requirements.txt

CMD [ "python3", "getExamples.py" ]

Build docker image called demo

>>> docker build -t bey .

Run docker image called demo

>>>docker run -t -i bey

Now, I’ll create a Docker compose file to run a Docker container using the Docker image we just created.

version: "3.6"
services:
app:
build: .
command: python getExamples.py
volumes:
- .:/pythonBeyonicExamples

Now we are going to run the following command from the same directory where the docker-compose.yml file is located. The docker compose up command will start and run the entire app.

docker compose up

### Output

NB: The screenshot below might differ according to your account deatils and your transcations in deatils.

To stop the container running on daemon mode use the below command.

docker compose stop

Output

Contributing to this repository. All contributions, bug reports, bug fixes, enhancements, and ideas are welcome, You can get in touch with me on twitter @HarunMbaabu.

Author: HarunMbaabu
Source Code: https://github.com/HarunMbaabu/BeyonicAPI-Python-Examples

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## JavaScript Algorithm: How to Reverse Linked List

When given a singly linked list how can we manage to reverse it? Like the following example, if the input linked list is 1->2->3->4->5->NULL, can we reverse it into the output as 5->4->3->2->1->NULL?

Example Input

Example Output

Each node of Linked list will have two attributes: value & next, and linked list will have head, tail and length attribute.

function ListNode(val, next) {
this.val = (val===undefined ? 0 : val)
this.next = (next===undefined ? null : next)
}

https://gist.github.com/GAierken/6e15c82f5e3457fa2d16e29400e130aa

There are two approaches to reverse a singly linked list: iterative and recursive.

1603450800

## Building a Singly Linked List

Most likely you arrived at this article because your preparation for an interview has lead you down a LeetCode rabbit hole. Linked lists are a favorite of many interviewers to test an interviewees understanding of basic data structures as well as your problem solving skills. Whether you’re just a bit rusty from school or this is your first time encountering linked lists they can be a bit tricky to understand at first.

As with most problems it is helpful to start with a diagram. A linked list is a linear data structure which can be thought of as a chain, where each link in a chain is connected to the next link. In a linked list, each link in the chain will be represented as a node.

In a singly linked list, each node contains some data and then a pointer to the next node. For a doubly linked list there would also be a pointer to the previous node. The first node in the list is conventionally referred to as the head and the final node’s next pointer refers to nothing. With this diagram constructed it is now time to start coding up a singly linked list in JavaScript.

### Coding a Node Class

Since a singly linked list consists of many notes it makes sense to create a class Node that way a new node can be easily and consistently instantiated. At the instantiation of a new node the data it will contain should be know but the next node might not be known.

Figure 2: JavaScript Node Class

A doubly linked list node class would look very similar to Figure 2 but with an additional property of previous that would also initialize to null as it may not be known or it could be the head node.