Data structures & algorithms
The patterns that show up over and over — arrays, hash maps, trees, and how to recognize which one fits.
17 lessons
Beginner
Big-O intuition — what the notation is actually telling youBeginner3 min read·Not startedArrays and strings — the basicsBeginner4 min read·Not startedLinked lists — the basicsBeginner3 min read·Not startedBasic sorting — how sorting actually worksBeginner4 min read·Not startedStacks and queues — the basicsBeginner4 min read·Not startedHash maps — the basicsBeginner4 min read·Not startedTrees — the basicsBeginner4 min read·Not started
Intermediate
The hash map pattern — turning O(n^2) into O(n)Intermediate3 min read·Not startedTwo pointers and sliding window, worked through a real problemIntermediate3 min read·Not startedRecursion and the call stackIntermediate4 min read·Not startedGraphs, BFS, and DFSIntermediate5 min read·Not startedHeaps and priority queuesIntermediate5 min read·Not startedGreedy algorithms — and when the locally best choice isn't enoughIntermediate5 min read·Not startedBacktracking — trying, and un-tryingIntermediate4 min read·Not startedTries — trees built for prefixesIntermediate4 min read·Not started