Welcome to Data Structures & Algorithms

Every course on this site teaches a specific language’s syntax. This course is different — it teaches ways of organizing data and solving problems that apply across every one of them. A data structure is a way of organizing data so it can be used efficiently; an algorithm is a step-by-step procedure for solving a problem. Understanding both is what separates code that merely works from code that works well as the amount of data grows.

This is also, realistically, the material technical interviews at most software companies focus on most heavily — not because day-to-day work is constantly implementing a sorting algorithm from scratch, but because it demonstrates a genuine understanding of how to reason about a program’s efficiency, a skill that transfers to every real system you will ever build.

Examples in this course

Code examples in this course are written in Python for readability — the concepts themselves apply identically in every language covered on this site. If Python is unfamiliar, the syntax used here is simple enough to follow even without having taken that course first, though it is a natural pairing.

Why “efficient” matters

# searching a list of 10 items vs 10 million items --n# the difference between these two approaches becomesn# enormous as the list grows, even though both are "correct"nif target in my_list:        # checks every item, one by onen    print("found")nnif target in my_set:         # near-instant, regardless of sizen    print("found")

Both lines above find the same answer. At 10 items, the difference is imperceptible. At 10 million items, one might take microseconds and the other might take seconds — the entire point of this course is learning to recognize and reason about that difference before it becomes a real production problem.

What you will build across this course

By the end of this course you will understand Big O notation for measuring efficiency, core data structures (stacks, queues, linked lists, trees, hash tables), searching and sorting algorithms, and recursion — the shared vocabulary and toolkit underlying every language on this site.