Theory

There are almost 3,000 problems on LeetCode. Blind 75, Blind 150, and other curated lists promise confidence—but the underlying structure matters more than any single list. After tagging problems by core technique, one discovery stood out: just 8 patterns cover over 2,000 problems. Not 80. Not 20. Eight. The 8 Patterns at a Glance # Pattern Problems Cumulative 1 Two Pointers 244 244 2 Sliding Window 164 408 3 Modified Binary Search 256 664 4 Hash Map / Hash Set 471 1,135 5 Monotonic Stack / Prefix Sum 170 1,305 …

Finding the median of two sorted arrays seems straightforward at first glance. However, this problem challenges you to achieve logarithmic time complexity, making it a favorite in coding interviews. Let’s explore different approaches and work toward the most efficient solution. Understanding the Problem You receive two sorted arrays in ascending order and need to find the median of the combined array. Mathematically, the median represents the middle element. For an odd number of elements, the median is the element at position . For an even number of elements, the median …

In this problem, we are given a matrix consisting of 0s and 1s. The goal is to update matrix and compute the distance of each cell containing 1 to the nearest 0. The distance between two adjacent cells is considered to be 1. The key challenge in this problem is efficiently determining the minimum distance for each cell while avoiding unnecessary computations. Input:mat = [[0,0,0], [0,1,0], [1,1,1]]Output:[[0, 0, 0], [0, 1, 0], [1, 2, 1]]Explanation:Each cell containing 1 is replaced by its shortest distance to the nearest 0. Brute Force …

Continuing with our System Design series we’ll be discussing message queue, an essential component in building scalable, decoupled systems. Message queues help systems handle communication between different parts asynchronously, ensuring smooth data flow even during heavy traffic. What is a Message Queue? A message queue is a system that allows different parts of a system to communicate with each other in an asynchronous manner. It acts as a buffer between a producer (the part that sends messages) and a consumer (the part that processes messages), allowing the producer to continue …

Let’s continue the journey in System Design. In this post, we’ll explore the concept of forward and reverse proxy, which play a crucial role in optimizing and securing web traffic. Proxies act as intermediaries, improving efficiency, security, and management of requests between clients and servers. What is a Proxy? A proxy is essentially an intermediary that sits between a client and a server, forwarding requests and responses between the two. It can be used for various purposes such as load balancing, security, caching, and more. Real-World Example: Imagine a bookstore …

Let us continue our System Design series! In this post, we’ll dive into the concept of indexing in databases. Indexing is a technique that allows for faster data retrieval by organizing and optimizing the way data is stored. What is Indexing? Indexing is like creating a shortcut for finding the right data quickly. Instead of scanning the entire database, the index helps you jump directly to the location of the data you need, improving the performance of your queries. Real-World Example: Let’s go back to our bookstore analogy. Imagine you …

Welcome again to System Design series! In this post, we will explore the concept of databases, which are fundamental to storing, organizing, and managing data in any application. Databases are the backbone of any data-driven system, providing the infrastructure needed to handle, retrieve, and manipulate data efficiently. What is a Database? A database allows users to easily access, manage, and update a structured collection of data. It serves as a digital ledger, storing information in an organized way, allowing quick retrieval and manipulation of data. Real-World Example: In our bookstore …

Welcome back to the System Design series! In this post, we will explore the concept of caching, a powerful technique used to enhance the speed and performance of applications. Caching plays a critical role in optimizing data retrieval and ensuring a smooth user experience. What is Caching? Caching is a technique where systems store frequently accessed data in a temporary storage area, known as a cache, to quickly serve future requests for the same data. This temporary storage is typically faster than accessing the original data source, making it ideal …

Boolean Algebra and introduction with examples. A key concept to determine logic in computer programming as well as mathematical problems.

A queue is a linear data structure working on First In First Out policy. But some use cases can require different solutions. We can create different queue types with the same basic idea. This post describes more about them