My Favorite Free Courses to Learn Data Structures and Algorithms In-Depth

Data structures and algorithms are the foundational building blocks of computer science and programming. They are the essential tools that allow us to write efficient, optimized code and solve complex problems. In the words of the famous computer scientist Niklaus Wirth, "Algorithms + Data Structures = Programs".

As a full-stack developer, I can confidently say that having a thorough understanding of data structures and algorithms is absolutely crucial. It‘s not just about acing coding interviews (although that‘s certainly important). On a day-to-day basis, I constantly find myself drawing upon my knowledge of data structures and algorithms to write better code, optimize performance, and solve tricky bugs.

Consider these statistics:

• A study by Triplebyte found that 48% of coding interview questions at top tech companies involve data structures and algorithms.
• HackerRank‘s 2020 Developer Skills Report found that 47% of developers say that data structures and algorithms are the most important skills for a developer to learn.
• In my experience, I estimate that I spend around 30-40% of my coding time working directly with data structures and algorithms.

So it‘s clear that if you want to be a successful, well-rounded developer, you can‘t afford to skimp on your data structures and algorithms knowledge. But how do you go about learning these topics, especially if you didn‘t focus on them much during your formal education?

Thankfully, there are a plethora of amazing free resources available online to learn data structures and algorithms in-depth. Here are some of my top recommendations:

1. Algorithms Specialization (Coursera)

Offered by: Stanford Online
Instructors: Robert Sedgewick, Kevin Wayne
Programming Language: Java
Skill Level: Intermediate
Courses: 4

This specialization, taught by the brilliant professors Robert Sedgewick and Kevin Wayne, is my top recommendation for anyone serious about mastering algorithms. It consists of four rigorous courses that cover essential data structures, algorithms, and analysis techniques in great depth.

Some key topics covered:

• Sorting algorithms (Quicksort, Mergesort, Heapsort)
• Searching algorithms (Binary search, BSTs, Red-black BSTs)
• Hash tables
• Graph algorithms (BFS, DFS, Dijkstra‘s shortest path, Prim‘s MST)
• Dynamic programming
• NP-completeness

The explanations are very clear and there are plenty of programming assignments in Java to reinforce your understanding. By the end, you‘ll have a solid grasp of key algorithms and data structures and be well-prepared for coding interviews. Over 500,000 students have enrolled in this top-rated specialization.

Best suited for: Intermediate developers with some coding experience looking to master algorithms.

2. Introduction to Algorithms (edX)

Offered by: MIT
Instructors: Erik Demaine, Srinivas Devadas
Programming Language: Python
Skill Level: Advanced
Estimated Effort: 12 hours per week

If you‘re looking for an authentic taste of MIT‘s rigorous computer science education, this free algorithms course is for you. Taught by MIT professors Erik Demaine and Srinivas Devadas, it dives deep into fundamental data structures and algorithms from an academic perspective.

Key topics include:

• Asymptotic analysis and Big O notation
• Sorting and searching
• Graph algorithms (BFS, DFS, shortest paths, minimum spanning trees)
• Dynamic programming
• Linear programming
• Intractability and NP-completeness

This course doesn‘t hold your hand – it‘s fast-paced, proof-heavy, and assumes significant mathematical maturity. But if you have the background and are looking to challenge yourself, you‘ll come away with an unparalleled understanding of algorithms and data structures.

Student quote: "Excellent detailed and rigorous treatment of algorithms and data structures, with the right balance of mathematics and practice." – Sharad A.

Best suited for: Advanced students and developers with strong math skills looking for academic rigor.

3. Intro to Data Structures and Algorithms (Udacity)

Offered by: Google
Instructor: Brynn Claypoole
Programming Language: Python
Skill Level: Beginner
Estimated Time: 4 months at 6 hours/week

This free course, developed by Google engineers, provides a fantastic introduction to fundamental data structures and algorithms for those just starting out. It covers key concepts like Big O notation, searching and sorting algorithms, and basic data structures, all with a focus on real-world applications.

Some key topics:

• Big O notation
• Searching algorithms (linear search, binary search)
• Sorting algorithms (bubble, merge, quick sort)
• Data structures (arrays, linked lists, stacks, queues, trees)
• Recursion
• Divide and conquer algorithms

All the coding examples and assignments are in Python, which is great for beginners thanks to its readability and simplicity. By the end, you‘ll be able to implement essential data structures and algorithms in Python and have a solid foundation for further learning.

Over 140,000 students have taken this highly-rated course. Udacity‘s signature "nanodegree" courses cost money, but this one is completely free.

Best suited for: Beginners, especially those interested in Python programming.

4. Data Structures and Algorithms Specialization (Coursera)

Offered by: UC San Diego, National Research University Higher School of Economics
Instructors: Daniel Kane, Alexander S. Kulikov, Michael Levin, Neil Rhodes
Programming Language: C++
Skill Level: Intermediate
Courses: 6

This comprehensive 6-course specialization, offered by UC San Diego and the Higher School of Economics, provides an excellent theoretical foundation in data structures and algorithms. It‘s more mathematically rigorous than some other courses, but still provides plenty of practical coding experience in C++.

Key topics covered:

• Big O notation
• Basic data structures (arrays, linked lists, stacks, queues)
• Dynamic arrays and amortized analysis
• Priority queues and heaps
• Hash tables
• Binary search trees
• Greedy algorithms
• Divide-and-conquer algorithms
• Dynamic programming
• Graph algorithms (BFS, DFS, shortest paths, minimum spanning trees)
• NP-completeness and heuristics

By the end, you‘ll have a solid grasp of the fundamental tools for designing efficient algorithms and be able to implement them in C++. With nearly 200,000 students enrolled, this is one of the most popular data structures and algorithms courses on Coursera.

Best suited for: Intermediate developers looking for a mix of theory and practice, especially those interested in C++.

5. JavaScript Algorithms and Data Structures Masterclass (freeCodeCamp)

Offered by: freeCodeCamp
Instructor: Colt Steele
Programming Language: JavaScript
Skill Level: Beginner to Intermediate
Estimated Time: 20 hours

Renowned instructor Colt Steele delivers a clear and engaging deep dive into algorithms and data structures from a JavaScript developer‘s perspective in this highly popular freeCodeCamp course. With nearly a million views on YouTube, this course has helped countless developers ace their interviews and become better programmers.

Key topics covered:

• Big O notation
• Analyzing performance of arrays and objects
• Problem solving approaches
• Recursion
• Searching algorithms (linear search, binary search, naive string search)
• Bubble sort, selection sort, insertion sort
• Merge sort, quick sort, radix sort
• Singly linked lists, doubly linked lists
• Stacks, queues
• Binary search trees, heaps, hash tables
• Graph traversal (BFS, DFS)
• Dijkstra‘s algorithm

The content is very accessible and easy to follow along with, but still conveys the essential concepts effectively. As a bonus, Colt is hilarious and keeps the course entertaining throughout. Whether you‘re a complete beginner or an experienced dev looking to brush up on the fundamentals, this is a great resource.

Best suited for: Anyone interested in learning data structures and algorithms in JavaScript, especially for interviews.

Honorable Mentions

While the above are my top recommendations, there are plenty of other excellent free data structures and algorithms courses available, such as:

• Algorithms, Part I and II by Princeton University (Coursera)
• Algorithms and Data Structures in Python (Udemy)
• Data Structures Concepts & Singly Linked List Implementation (Udemy)
• Data Structures Easy to Advanced Course (freeCodeCamp)
• Easy to Advanced Data Structures (Udemy)

Beyond Online Courses

Of course, no online course alone will make you a data structures and algorithms master. I strongly encourage you to supplement your learning with other resources, such as:

• Books (some top recommendations: "Introduction to Algorithms" by CLRS, "Algorithm Design Manual" by Steven Skiena, "Elements of Programming Interviews" by Adnan Aziz)
• Coding practice websites (LeetCode, HackerRank, CodeChef, Project Euler)
• Implementing data structures and algorithms yourself in your language of choice
• Participating in coding competitions (Google CodeJam, Facebook HackerCup, TopCoder)

Conclusion

Data structures and algorithms are absolutely essential knowledge for all developers, regardless of specialization or years of experience. Understanding these fundamental computer science concepts deeply will make you a much stronger programmer and problem solver.

Thankfully, with the rise of MOOCs and online learning platforms, it‘s never been easier to gain this foundational knowledge for free through self-study. The courses highlighted in this article are an excellent starting point.

Remember, the key to mastering data structures and algorithms is consistent practice and application. Don‘t just passively watch video lectures – make sure you‘re coding along, doing assignments, and challenging yourself to solve difficult problems. That‘s the only way the knowledge will truly stick.

If you put in the time and effort to thoroughly learn data structures and algorithms through these free online courses and supplemental resources, you‘ll stand out from the crowd as an exceptional, well-rounded developer. Opportunity awaits!