gognlin / leetcode-patterns

A curated list of 160+ leetcode questions grouped by their common patterns

Home Page:https://seanprashad.com/leetcode-patterns/

Geek Repo:Geek Repo

Github PK Tool:Github PK Tool

Leetcode Patterns

Table of Contents


This repo is intended for any individual wanting to improve their problem solving skills for software engineering interviews.

Problems are grouped under their respective subtopic, in order to focus on repeatedly applying common patterns rather than randomly tackling questions.

All questions are available on leetcode.com with some requiring leetcode premium.


It is highly recommended to read chapters 1, 2, 3, 4, 8, and 10 of Cracking The Coding Interview to familiarize yourself with the following data structures and their operations:

  • Arrays
  • Maps
  • Linked Lists
  • Queues
  • Heaps
  • Stacks
  • Trees
  • Graphs

In addition, you should have a good grasp on common algorithms such as:

  • Breadth-first search
  • Depth-first search
  • Binary search
  • Recursion


This pdf contains useful information for the built-in data structures in Java.

Other useful methods to know include substring(), toCharArray(), Math.max(), Math.min(), and Arrays.fill().

Question List

The entire question list can be found here: https://seanprashad.com/leetcode-patterns/.

In addition to viewing the question list, companies that have previously asked the question in the past 6 months (as of January 2020) will be listed. You can also use the checkboxes to mark which questions you've completed!


Solutions written in Java can be found in the solutions branch.

Leetcode Discuss

Leetcode discuss is an amazing resource and features previous interview questions, as well as compensation and general career advice.

Tips to Consider

If input array is sorted then
    - Binary search
    - Two pointers

If asked for all permutations/subsets then
    - Backtracking

If given a tree then
    - DFS
    - BFS

If given a graph then
    - DFS
    - BFS

If given a linked list then
    - Two pointers

If recursion is banned then
    - Stack

If asked for maximum/minumum subarray/subset/options then
    - Dynamic programming

If asked for top/least K items then
    - Heap

If asked for common strings then
    - Map
    - Trie

    - Map/Set for O(1) time & O(n) space
    - Sort input for O(nlogn) time and O(1) space


Think a question should/shouldn't be included? Wish there was another feature? Feel free to open an issue with your suggestion!


This list is heavily inspired from Grokking the Coding Interview with additional problems extracted from the Blind 75 list and this medium article on 14 patterns to ace any coding interview question.

ezoic increase your site revenue


A curated list of 160+ leetcode questions grouped by their common patterns


License:GNU General Public License v3.0


Language:JavaScript 96.7%Language:SCSS 2.4%Language:HTML 0.9%