The O(n) Club: Two Sum IV – The BST Showdown You Didn’t Know You Needed
The O(n) Club: Two Sum IV – The BST Showdown You Didn’t Know You Needed ⚡ TL;DR Given a binary search tree and a target k, does any pair…
The O(n) Club: Jewels and Stones — HashSet Heroics for the Chronically Loopy
The O(n) Club: Jewels and Stones — HashSet Heroics for the Chronically Loopy ⚡ TL;DR You have a string of jewels (unique, case-sensitive,…
The O(n) Club: Word Ladder II – BFS, DFS, and the Great Shortest-Path Scavenger Hunt
The O(n) Club: Word Ladder II – BFS, DFS, and the Great Shortest-Path Scavenger Hunt ⚡ TL;DR You need to find all the shortest word ladders…
The O(n) Club: Longest Substring with At Least K Repeating Characters — Chop Shop Edition
The O(n) Club: Longest Substring with At Least K Repeating Characters — Chop Shop Edition ⚡ TL;DR Your PM says, “Give me the longest…
The O(n) Club: Ugly Numbers II – Three Pointers, Zero Ugly Bugs
The O(n) Club: Ugly Numbers II – Three Pointers, Zero Ugly Bugs ⚡ TL;DR Ugly numbers are those rare creatures with only 2, 3, or 5 as their…
The O(n) Club: Sort Characters By Frequency — and Stop Overengineering It
The O(n) Club: Sort Characters By Frequency — and Stop Overengineering It ⚡ TL;DR Your job: shuffle the string so that characters with the…
The O(n) Club: Become the Overlord of Longest Repeating Character Replacements (Sliding Window Style)
The O(n) Club: Become the Overlord of Longest Repeating Character Replacements (Sliding Window Style) ⚡ TL;DR Here’s the interview…
The O(n) Club: Valid Anagram, or How to Make Your Strings Get Along Without Therapy
The O(n) Club: Valid Anagram, or How to Make Your Strings Get Along Without Therapy ⚡ TL;DR Quick test: Are "listen" and…
The O(n) Club: Top K Frequent Words—How To Count, Sort, and Not Cry
The O(n) Club: Top K Frequent Words—How To Count, Sort, and Not Cry ⚡ TL;DR Count each word. Sort the results by how often each word shows up…
The O(n) Club: Permutation in String — Where Brute Force Goes To Die
The O(n) Club: Permutation in String — Where Brute Force Goes To Die ⚡ TL;DR Given two strings, does s2 have a substring that’s a…