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System Design

• Whatsapp System Design

• Instagram System Design

• Design an URL shortening service like bit.ly

• Unique ID Generation System Design

• Design an In-Memory Cache

• LRU Cache Design

• Design a Vending Machine

• ATM Machine System Design

• Interview Question: Design an Object Pool

• System Design of Tic Tac Toe Game

• What does Strong Consistency mean in Database

• CAP Theorem in Distributed Systems

• Pastebin System Design

• Parking Lot System Design

• Design a hit counter

• Chess Game System Design

• Design a Leaderboard or Low-Level Design of a Leaderboard

• Nearby Friends System Design

• System Design of Snake and Ladder game
  
• LFU Cache Design and Implementation

• What is Virtual IP

Generic Articles

• Understanding Base64 encoding/decoding

• What is Virtual IP

• Point to Point (P2P) vs Pub/Sub in Distributed Message Queue

Sharding

• Understanding Directory-Based Sharding

Linux Terminal

• Unset an env variable in terminal or bash

• Difference between “./”, “.” and source in BASH shell or terminal (Linux)

• How to create an environment variable for tomcat on Linux?

• Difference between soft links and hard links on Linux

• How to go a particular line in a file when using vi or vim (Linux)

• Clear terminal screen on Mac- Non Scrollable

• How to go at last line of a file in linux

• How to set line numbers in a file using vi or vim (Linux)

• How to delete contents of a file using vi or vim in bash/terminal (Linux)

• How to redirect output/errors of a command to a file on Linux

• How to run a command in the background and switch it back to the foreground on Linux

• How to run commands on remote servers using SSH

• How to find size of file or directory on Linux

• How to find the size/space of disks and volumes attached to the server

• Check which process is using port 8080 on your localhost on MAC or Linux

• How to handle failure in a command in bash or terminal

• What does chmod o+w command mean in bash or terminal

• Generate UUID without a dash in the terminal in MAC OS

• What does chmod o-w command mean in bash or terminal

• Grep two words together in terminal

• What does the set -e command do

• Abort or exit a shell script if any command fails

• How to find what /bin/sh points to on your machine

• Know the current user on Linux

• Check all groups that current logged in user belong to on Linux

AWS

• How to increase the size of an EBS volume in EC2 with the help of cloud formation.

Python

• How to run os commands in python and read its output

• How to read a file in python

• How to login in perforce(p4 command line) in python

Ruby HTTP

• Convert Query Param String to Query Param Hash in Ruby Language

• Extract a URL from a string in Ruby Language

• Parse a URL and extract all the parts in Ruby Language

• Get full hostname and port from a URL in Ruby Language

• Get or Extract Query Params from a URL in Ruby Language

Ruby File/Folder Operations

• Check if a file is writable or not in Ruby language

• JSON parse a file or string in Ruby Language

• Check if a file exists in Ruby Language

Ruby Generic

• Run Ruby language code in command line or terminal – Single-line and Multiline

• Execute System Commands in Ruby Language

• Turn a file path into a hyperlink in the terminal in RubyMine using Ruby Language

• Print/Output color in the console in Ruby Language

• Load a .env or environment file in Ruby Language

• Print/Output text in bold in Ruby Language

• Print/Output text in italic in Ruby Language

• Fix LoadError cannot load such file — e2mmap in Ruby 2.7.0

• Fix LoadError cannot load such file — scanf in Ruby 2.7.0

• Ruby convert string to bool

Ruby Regex or Regular Expression

• Ruby Regex or Regular Expression in a variable

• Ruby Regex: Match any character in Regular Expression

• Ruby regex match in an if check

Ruby Arrays

• Traverse three arrays together in Ruby Language

Ruby Hash

• Delete a nested key in a hash in Ruby Language

Regex

• Understanding Curly Braces in Regular Expressions or Regex

Array

• Wildcard matching or regex matching problem

• Group anagrams together program

• Jump Game Program

• Program to remove duplicates from a sorted array

• Maximum continuous subarray sum program

• Largest Rectangular Area in a Histogram

• Program for Combination Sum Problem

• Program for Power set of a given array of integers

• Program to merge two sorted arrays

• Remove all occurrences of a given value in an array in place

• Unique Paths Program

• Best time to Buy-Sell Stocks Program

• Search Insert Position Program

• Find All Duplicates in an Array

• Find all Arithmetic series of length greater than two

• Distinct or Unique Permutations of a string or array

• Non-Overlapping intervals program

• Two furthest houses with different colors

• Maximum Difference between increasing elements in an array

• Maximum Length of Contiguous Subarray with an equal number of 0’s and 1’s

• Program for Binary Search in a sorted array

• Majority element in an array

• Find the number which appears once in an array

• Longest Consecutive Sequence Program

• Check If N and Its Double Exist

• Program for Income Tax Paid

Tree

• Check if a given tree is a Binary Search Tree

• Program for the height of a binary tree

• Inorder traversal of a Binary Tree

• Postorder traversal of a Binary Tree

• Preorder traversal of a Binary Tree

• Same binary tree program

• Print all Binary Tree Paths

• Binary Tree Maximum Path Sum Program

Binary Search Tree

• Program for Sorted Array to Height Balanced BST

• Recover Binary Search Tree Program

Dynamic Programming

• Interleaving String Program

• Program for Length of Longest Increasing Subsequence

• Range Sum Array Program

• Range Sum 2d array program

• Count Possible Decodings of a digit sequence into letters

• Minimum Path Sum Program

• Program for House Robber Problem

• Program for Pascal’s Triangle

String

• Add two binary numbers program

• Check if two given strings are anagrams

• Program to find if a given sub string exists

• Reverse Words in a sentence

• Letter Combinations of a Phone Number Program

• Program for length of the last word in a string

• Program to multiply two strings

• Program for the total number of words in a sentence

• Maximum words in a group of sentences

• Kth Distinct String in an Array Program

• Longest Common Prefix in a set of strings

• Program to Reverse vowels of a string

• Sort characters by frequency

• Program for Longest Word in Dictionary through Deleting

Integers

• Add all digits of a number program

• Program to divide two integers without using multiplication or division operator

• Program to calculate the power of a number

• Plus one program or Add one to an integer array

• The nth digit in a sequence program

• Program for an ugly number

• Program for ugly number 2 in Go (Golang)

Linked List

• Program to check if a given linked list has a cycle

• Program to Rotate a linked list

• Program to detect cycle start node in a linked list

• Remove nth node from the end in a linked list

• Delete middle node of a linked list

• Program to Partition a linked list

• Remove Linked List Elements Program

Matrix

• Set matrix zero if a row or column is zero

• Rotting Oranges Program

• Determine Whether Matrix Can Be Obtained By Rotation

• Count unguarded cells program

Graph

• Count unreachable pair of nodes in an undirected graph

• Detonate the maximum bombs program

• Is Graph Bipartite Program

ZSH

• zsh: no matches found: HEAD^

MAC OS

• How to make any folder a favorite in MAC OS

Jupyter Notebook

• Jupyter notebook “Schema Not Found” 404 error