Trie cheatsheet for coding interviews
Introduction​
Tries are special trees (prefix trees) that make searching and storing strings more efficient. Tries have many practical applications, such as conducting searches and providing autocomplete. It is helpful to know these common applications so that you can easily identify when a problem can be efficiently solved using a trie.
Be familiar with implementing from scratch, a Trie class and its add, remove and search methods.
Learning resources​
- Readings
- Trying to Understand Tries, basecs
- Implement Trie (Prefix Tree), LeetCode
- Additional (only if you have time)
Time complexity​
m is the length of the string used in the operation.
| Operation | Big-O |
|---|---|
| Search | O(m) |
| Insert | O(m) |
| Remove | O(m) |
Corner cases​
- Searching for a string in an empty trie
- Inserting empty strings into a trie
Techniques​
Sometimes preprocessing a dictionary of words (given in a list) into a trie, will improve the efficiency of searching for a word of length k, among n words. Searching becomes O(k) instead of O(n).
Essential questions​
These are essential questions to practice if you're studying for this topic.
Recommended practice questions​
These are recommended questions to practice after you have studied for the topic and have practiced the essential questions.
Recommended courses​
AlgoMonster​
AlgoMonster aims to help you ace the technical interview in the shortest time possible. By Google engineers, AlgoMonster uses a data-driven approach to teach you the most useful key question patterns and has contents to help you quickly revise basic data structures and algorithms. Best of all, AlgoMonster is not subscription-based - pay a one-time fee and get lifetime access. Join today for a 70% discount →
Grokking the Coding Interview: Patterns for Coding Questions​
This course on by Design Gurus expands upon the questions on the recommended practice questions but approaches the practicing from a questions pattern perspective, which is an approach I also agree with for learning and have personally used to get better at coding interviews. The course allows you to practice selected questions in Java, Python, C++, JavaScript and also provides sample solutions in those languages along with step-by-step visualizations. Learn and understand patterns, not memorize answers! Get lifetime access now →
Master the Coding Interview: Data Structures + Algorithms​
This Udemy bestseller is one of the highest-rated interview preparation course (4.6 stars, 21.5k ratings, 135k students) and packs 19 hours worth of contents into it. Like Tech Interview Handbook, it goes beyond coding interviews and covers resume, non-technical interviews, negotiations. It's an all-in-one package! Note that JavaScript is being used for the coding demos. Check it out →