Dutch national flag problem in Javascript

Image
Dutch national flag problem and solution in Javascript Problem statement:   The Dutch national flag (DNF) problem is one of the most popular programming problems proposed by Edsger Dijkstra. The flag of the Netherlands consists of three colors: white, red, and blue. The task is to randomly arrange balls of white, red, and blue such that balls of the same color are placed together. Now, let's consider an array with 3 distinct values say 0, 1 and 2. We won't be using any sort method and we need to sort this array in 0(n). Input Array :  let   arr  = [ 0 ,  2 ,  1 ,  0 ,  1 ,  2 ,  0 ,  2 ]; Expected Output: [ 0, 0, 0, 1, 1, 2, 2, 2 ] Solution Approach : When we see expected output, we can clearly see that sorted array is divided into 3 sections having values 0 , 1 and 2. So, let's divide the array in 3 sections: a) from 0th index to left boundary b) from left boundary to right boundary c) from right boundary to last index. Now we will create 2 pointers : left (starting from 0
Post a Comment

Create Telegram Bot using Nodejs in 10 minutes

Have you ever thought of creating a telegram bot for sending some useful information, news, alerts, images or even reminders, but didn't know where to start from.

Well, in this tutorial we will create a Telegram BOT and will send a chat message from the BOT to user, and NodeJS will be used for the coding part. The best part is i will share the exact simple steps that you need to perform and it won't take more than 10 mins to setup your first telegram bot and to send first message to the user from the NodeJS code.

Step 1: Create your first Telegram Bot

Telegram has a bot to create the bots, just search the BotFather and then follow the instructions to create a BOT.

  • Use the /newbot command to create a new bot. The BotFather will ask you for a name and username, then generate an authorization token for your new bot.
  • The name of your bot is displayed in contact details and elsewhere.
  • The Username is a short name, to be used in mentions and t.me links.
  • The token is a string along the lines of 110201543:AAHdqTcvCH1vGWJxfSeQfSBs0K5PALD(sample token) that is required to authorize the bot and send requests to the Bot API. Keep your token secure and store it safely, it can be used by anyone to control your bot.
Step 2: Message your Bot 

Search your newly created Bot on Telegram and message '/start'. This is required to get your chat id so that Bot can contact/message you back.

Step 3: Retrieve Chat ID

For this we will use Telegram API provided with your bot token. Just enter the below given URL in postman/chrome and you will get the chat id in response (highlighted in sample response).

API URL:  https://api.telegram.org/bot<bot-token>/getUpdates

Sample request:   https://api.telegram.org/bot9234516987:PQFZkFrnoCoFjJD4Qj3LdRpM1RxFA_k91YG/getUpdates
Sample response:
 {"ok":true,"result":[{"update_id":123456789,
"message":{"message_id":1,
"from":{"id":234567890,"is_bot":false,"first_name":"Test-user","language_code":"en"},
"chat":{"id":234567890,"first_name":"Tes-user","type":"private"},
"date":234567890,"text":"/start",
"entities":[{"offset":0,"length":6,"type":"bot_command"}]}}]}

Step 4 : Send Message to yourself from the Bot

For this we will use Telegram API provided with your bot token and the chat id (from step 3).
  • We will use "axios" for sending the API request so download the module : 
            npm install axios
  • Create your index.js file and add below line :
            const axios = require("axios").default;
  • Add the below code to call the telegram API (Replace values of <BOT_TOKEN> and <CHAT_ID> with the values generated in step 1 and 3 respectively )
    axios
    .get(
      'https://api.telegram.org/bot<BOT_TOKEN>/sendMessage?chat_id=<CHAT_ID>&text=Hello'
    )
    .then((response) => {
      // handle success
      console.log("message sent " + JSON.stringify(response.data));
    })
    .catch(function (error) {
      // handle error
      console.log(error);
    });
  
  • Execute the js file with : node index.js    

  Sample response:
  {"ok":true,
"result":{"message_id":2,"from":{"id":234567890,"is_bot":true,"first_name":"<BOT name>","username":"<BOT username>"},"chat":{"id":234567890,"first_name":"test-user","type":"private"},"date":234567890,"text":"Hello"}}    

  • Check in the chat of your telegram bot, you would have received "Hello" from your Bot.
CONGRATS!!, you have now successfully sent a message to yourself from your Telegram Bot. Well, this is just the start, now you can create infinite number of exciting and useful projects/utilities using Telegram Bot. This tutorial was just to help you setting up your first BOT and making first API request using the code.
Also, don't forget to check official API documentation of Telegram Bots to find more details. 

Comments

Post a Comment

Popular posts from this blog

Ice Cream Parlor : Hackerrank Problem and Solution

Ice Cream Parlor : Hackerrank Problem  Each time Sunny and Johnny take a trip to the Ice Cream Parlor, they pool together   dollars for ice cream. On any given day, the parlor offers a line of   flavors. Each flavor,  , is numbered sequentially with a unique ID number from   to   and has a cost,  , associated with it. Given the value of   and the cost of each flavor for   trips to the Ice Cream Parlor, help Sunny and Johnny choose two flavors such that they spend their entire pool of money ( ) during each visit. For each trip to the parlor, print the ID numbers for the two types of ice cream that Sunny and Johnny purchase as two space-separated integers on a new line. You must print the smaller ID first and the larger ID second. Note:  Two ice creams having unique IDs   and    may  have the same cost (i.e.,  ). Input Format The first line contains an integer,  , denoting the number of trips to the ice cream parlor. The   subsequent lines describe all of Sunny
Read more

Javascript Problem: Find the next perfect square!!

Codewars   Problem and solution with approach explained       Objective:   In this challenge, we will solve the “Find the next perfect square!”  Codewars   puzzle using  javascript .   Problem statement:   You might know some pretty large perfect squares. But what about the NEXT one?   Complete the  findNextSquare   method that finds the next integral perfect square after the one passed as a parameter. Recall that an integral perfect square is an integer n such that sqrt(n) is also an integer.   If the parameter is itself not a perfect square then -1  should be returned. You may assume the parameter is positive.   Examples:   findNextSquare (121) --> returns 144    findNextSquare (625) --> returns 676    findNextSquare (114) --> returns -1 since 114 is not a perfect   Solution Approach:   Step 1: check if the perfect square root of the given number say “n” is available.   Step 2: if yes, then simply get the square of the “n+1” number.   Step 3: if no, return false.   Keeping t
Read more

Disemvowel Trolls || Codewars problem and solution in Javascript || Topic : Strings and RegEx

  Problem: Disemvowel Trolls Description : Trolls are attacking your comment section! A common way to deal with this situation is to remove all of the vowels from the trolls' comments, neutralizing the threat. Your task is to write a function that takes a string and return a new string with all vowels removed. For example, the string "This website is for losers LOL!" would become "Ths wbst s fr lsrs LL!".   Solution 1# function disemvowel(str) {   var str = str.replace(/a/gi,'').replace(/e/gi,'').replace(/i/gi,'').replace(/o/gi,'').replace(/u/gi,'');   return str; } Solution 2# (slightly more concise) function disemvowel(str) {   return str.replace(/[aeiou]/gi, ''); }
Read more