leetcode.md

leetcode

Let's learn about Leetcode via these 72 free blog posts. They are ordered by HackerNoon reader engagement data. Visit the /Learn or LearnRepo.com to find the most read blog posts about any technology.

LeetCode is an online platform offering a vast collection of coding challenges and algorithmic problems. It helps developers hone their coding skills, prepare for technical interviews, and improve problem-solving proficiency, making it essential for career advancement.

1. 14 Patterns to Ace Any Coding Interview Question

The process of preparing for coding interviews is anxiety-inducing for many developers. There’s so much material to cover, and often much of it feels irrelevant to what devs are doing in their day jobs, which only adds to the stress.

2. Java Algorithms: Merge k Sorted Lists (LeetCode)

An easy approach to the hard leetcode problem Merge k Sorted Lists from that many people using Java Algorithms will need to learn in order to be effective.

3. Java Algorithms: Linked List in Binary Tree (LeetCode)

Linked List in Binary Tree

4. Implementing a Singly or Doubly Linked List in Java (A LeetCode Question)

Design your implementation of the linked list. You can choose to use a singly or doubly linked list.

5. How to Implement Trie (Prefix Tree) - Blind 75 LeetCode Questions

A trie (pronounced as “try”) or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings.

6. How To Merge Two Sorted Lists

We can use LinkedList to merge both sorted lists, though there are considerations to doing it single or double-linked that may complicate the operation.

7. Java Algorithms: Coding a Binary Tree Right Side View (LeetCode)

In this article, you will learn how to code a Binary Tree Right side view in LeetCode.

8. How to Solve Number of Islands From Blind 75 LeetCode Questions

We will learn how to solve "Number of Islands" from Blind 75 LeetCode Questions.

9. How to Find the Product of All Elements in an Array Except Self - Blind 75 LeetCode

How to Find the Product of All Elements in an Array Except Self? You must write an algorithm that runs in O(n) time and without using the division operation.

10. Java Algorithms: Copying List with Random Pointer (LeetCode)

A linked list of length n is given such that each node contains an additional random pointer, which could point to any node in the list, or null.

11. Clone Graph Blind75 LeetCode Problem

Clone Graph Blind75 LeetCode Problem

12. Merge Intervals in Java Algorithms (LeetCode)

Returning an array of the non-overlapping intervals that span every input interval.

13. Validate Binary Search Tree Blind 75 LeetCode Question

Given the root of a binary tree, determine if it is a valid binary search tree (BST

14. Comparing Coding Platforms: LeetCode, CodeWars, CodeSignal, and HackerRank

Exploring coding platforms: My insights and experiences shared. Discover the pros and cons of informed choices. Join me on this insightful journey!

15. Optimizing List Manipulation: Two Pointers Technique

"Optimizing List Manipulation: Two Pointers Technique" explores the effective application of the two-pointer technique to efficiently manipulate lists, reducing

16. 5 to 23 Patterns to Ace Any Coding Interview

How to prep for coding interviews by using patterns to figure out how to guess the most likely questions to be asked in many programming job interviews.

17. LLMs vs Leetcode (Part 1 & 2): Understanding Transformers' Solutions to Algorithmic Problems

Dive deep into the world of Transformer models and algorithmic understanding in neural networks.

18. Understanding the Sliding Window Pattern: Efficient Utilization Through Examples

The article explores the Sliding Window pattern's efficient application through illustrative examples.

19. Java Algorithms: First Missing Positive (LeetCode)

The First Missing Positive problem is an algorithm problem that requires finding the smallest positive integer that is not present in a given unsorted array of

20. How to Go From Noob to Master: Leetcode Contests

How to Master Data Structures and Algorithms and Leetcode and Codeforces Contests for Beginners.

21. 10 LeetCode Patterns to Solve 1000 LeetCode Problems

Ever wondered how to master 1000 LeetCode problems in six months? You have a shortcut. By learning these ten patterns, you can solve LeetCode easily.

22. Empowering Newbies: Building Confidence Through 600+ LeetCode Solutions – A Guide for Beginners

Discover valuable insights on tackling over 600 LeetCode problems. Gain practical advice and useful resources for mastering coding interviews successfully.

23. Testing LLMs on Solving Leetcode Problems

Large-scale test with Gemini Pro 1.0 and 1.5, Claude Opus, and ChatGPT-4 on hundreds of real algorithmic problems.

24. Backtracking LeetCode Pattern: Permutations vs Subsets in Java

With the help of the backtracking algorithm, I will solve the permutations and subsets problems in Java that are frequently used during job interviews.

25. 30 Days DSA Interview Preparation Plan

All data structures and algorithms concepts and solutions to various problems in Python3 stored in a structured manner to prepare for coding interviews.

26. Testing LLMs on Solving Leetcode Problems in 2025

Large-scale LLMs test (o1, o3-mini; Gemini 2.0 Flash, 2.0 Pro, 2.5 Pro; DeepSeek V3, R1; xAI Grok; Claude 3.7 Sonnet) on solving Leetcode algorithmic problems

27. ChatGPT-4 Solves 85% of Leetcode Easy Problems

This article aims to find out how much of ChatGPT's performance is "problem-solving ability" versus sheer randomness or “memorization of the correct solution.

28. Kth Largest Element in an Array - Quickselect Using Lomuto Partitioning Scheme.

Solving k-th largest element in the array using heap and quickselect

29. A Chrome Extension to Code Daily with LeetCode

I made a Chrome extension that generates random LeetCode questions for you to practice with every day. Here's how I did it.

30. Comparing LLMs' Coding Abilities Across Programming Languages

Benchmark of 5 LLMs solving LeetCode problems in Python, Java, Rust, Elixir, Oracle SQL and MySQL. Results show language popularity correlates with success.

31. Mastering Leetcode: 6 Problem Picking Patterns for Technical Success

Coding Ninja Says: Accelerate your career by solving leetcode analysis paralysis with additional career advice

32. Multiply Strings (LeetCode): An Out of the Box Solution In JavaScript

Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.

33. Why Making LeetCode a Daily Habit Is the Key to Skill Development and Career Growth

In this article, I want to share a great life hack on how to always stay afloat in the IT market and keep yourself in shape by spending 10-30 minutes a day

34. The Math Behind the Bulb Switcher Challenge: How Many Bulbs Will Remain On After N Rounds?

This article describes several solutions and approaches to the "Bulb Switcher" problem.

35. Solving LeetCode Problems Using Graph Theory

Graphs model pairwise relationships with vertices and edges.

36. Graduating from Leetcode

Leetcode.com is a website where people–mostly software engineers–practice their coding skills. It’s pretty similar to sites like HackerRank & Topcoder which will rank your code written for a particular problem against the ones submitted by other users.

37. How to Use Kotlin to Solve Coding Problems

I have talked to many Android developers, and most of them are excited about Kotlin. So am I. When I just started learning Kotlin, I was solving Kotlin Koans, and along with other great features, I was impressed with the power of functions for performing operations on collections. Since then, I spent three years writing Kotlin code but rarely utilised all the potential of the language.

38. Implement Stack using Queues

How to implement a last-in-first-out (LIFO) stack using only two queues and why you should use this method based on a set of questions found on Leetcode.

39. Finding Product of Array Except Self

Sergei Golitsyn. Find the product of all the elements of nums except nums[i]. The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit int

40. Binary Lifting and Its Applications

Binary Lifting and its use in finding Lowest Common Ancestor (LCA). Explore this amazing algorithm that speeds up ancestor queries in the tree data structure.

41. How to Solve the Hamming Distance Problem in C++, A Google Interview Question

In hamming distance problem, we find the number of positions where the bits are different for the given input with constant time complexity.

42. Mastering Top LeetCode Patterns for Coding Interviews: A 2025 Guide and Strategy

Master 7 key LeetCode patterns (Sliding Window, Two Pointers, DP & more) for 2025 coding interviews. Includes code examples & 12-week study plan.

43. Kotlin Binary Tree Preorder Traversal (A Recursive Solution and Without Using Recursion)

This post is about preorder traversal of a binary tree, a method of traversing the tree in which the current node is visited before its children.

44. Contains Duplicate and Missing Number

author: Sergei Golitsyn https://t.me/crack_code_interview

1. return true if any value appears at least twice
2. number in the range that is missing from arr

45. House Robber

You need to solve this: given an integer array nums representing the amount of money of each house, return the maximum amount of money you can rob tonight.

46. Do Not Fear Dynamic Programming (Part 1)

Dyanmic Programming isn't as hard as people think. We'll break it down in this guide.

47. Is a Given Number the Power of 2?

In this lesson, we will try to check if the given number is a power of 2. We solve this by writing an efficient algorithm that takes an optimal amount of time.

48. Implement Queue using Stacks

author: Sergei Golitsyn Implement a first in first out (FIFO) queue using only two stacks

49. 87 Stories To Learn About Data Structures

Learn everything you need to know about Data Structures via these 87 free HackerNoon stories.

50. Leetcode or Projects — Which One Is Likely to Land You a Tech Job?

If your résumé has no strong projects, you might get rejected. On the flip side, if you haven’t done any interview prep, you might bomb the actual interviews.

51. Using the Two-Pointer Kotlin Approach to Solve for the Container with the Most Water

This problem asks us to find the maximum amount of water that can be stored in a container formed by two lines, on a 2-dimensional plane and the x-axis.

52. Power of Four and Reverse Vowels of a String

The easiest way how to solve this problem is to divide N on 4 and that is it.

53. Leetcode Coding Challenge Using Lambda

I am a big fan of leet code so when we decided to have a code challenge in our team I thought it wouldn’t be a bad idea to build one which should include pretty basic functionalities like:

54. Implementing Stack Using Queue

Sergei Golitsyn. Implement a last-in-first-out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal stack.

55. Find the Celebrity

A celebrity is known to everyone, but he does not know anyone at the party.

56. My Open Source Project: The DSA Guide for Data Structures and Algorithms Students

DSA-Guide: Guide to DSA Problem for Leetcode, Codechef, CSES, GFG

57. How I Train Myself For Google Internship Interview

I recently got an intern offer from Google for Summer 2020. I have been practicing LeetCode problems for more than two years. Other than the LC problems, I have used the educative courses to help me prepare the coding interviews.

58. 7 Tips for Grinding Leetcode

Leetcode is famous for being a perfect platform for practicing coding problems and to master coding interviews, unlike others, it is not for competitive program

59. Solving The Staircase Problem With Just 5 Lines

The staircase problem is a challenging and well-studied problem that may stump beginners. However, experienced developers can solve it in just five lines.

60. Breaking Barriers: My First Step into the World of Blogging

I am introducing myself. This will be the start of my blogging journey.

61. How to Check If Your Point Is Reachable: A JavaScript Algorithms Guide

62. IP Address Restoration in Kotlin

This post is about providing a solution in Kotlin for finding all valid IP addresses that can be formed by inserting dots into a given string of digits.

63. Leetcode Problem Hacks: 881 Boats to Save People

I dive into LeetCode problem: 881, Boats to Save People. I try to use Count Sort to optimize my solution.

64. Grokking Dynamic Programming (Part 2)

Part 2 on my series about dynamic programming problems and coding techniques to solve them.

65. Convert Sorted Array to Binary Search Tree

Using Kotlin at your technical interviews!

66. The LeetCode Illusion: Why Coding Interviews Don't Measure Engineering Skill

LeetCode interviews measure pattern recall, not engineering skill. Here's why the old model is broken, and what better hiring actually looks like.

67. Reflecting on My Year of Consistent Leetcode Practice and Mistakes to Avoid

A year of consistent leetcode practice in improving problem solving skills

68. My Dev Journey in 2023: A Year in Review

Reflecting on 2023 with my accomplishments and programming goals and seeing where 2024 takes me.

69. How to Keep Track of Daily LeetCode Challenges With Todoist and Cloudflare Worker

Automate your daily task with Cloudflare Worker's Cron job with an example using LeetCode and Todoist. Test Cloudflare worker cron trigger using Miniflare.

70. Most Coding Interview Advice Gets This Wrong

Learn how to succeed in coding interviews by clarifying the problem, thinking out loud, coding cleanly, and handling getting stuck.

71. The HackerNoon Newsletter: Testing LLMs on Solving Leetcode Problems in 2025 (4/8/2025)

4/8/2025: Top 5 stories on the HackerNoon homepage!

72. The “Grind LeetCode” Advice is Mathematically Stupid (I Scraped 1,500 Questions to Prove It)

I scraped 1500+ tech interview questions to expose company biases. Stop paying $35/mo for LeetCode Premium. Search your target company's exact data for free.