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Data Structures & Algorithms

Ordered by dependency, not by topic popularity. Each chapter states what you should be able to do afterwards, then checks it.

Complexity, core structures, and the techniques that build on them

01
Complexity Analysis
How to reason about cost before you write code, and why the answer is never measured in seconds.
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Arrays

Contiguous storage, the operations it makes cheap, and the ones it makes expensive.

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Strings

Text as a sequence, the cost of immutability, and the patterns that recur in string problems.

Hash Tables

The structure behind most quadratic-to-linear improvements, and when it is the wrong tool.

Two Pointers

Two indices moving under a rule that never lets either of them backtrack.

Sliding Window

A contiguous range that grows and shrinks instead of being rebuilt.

Binary Search

Halving a space using a yes/no question that flips exactly once.

Linked Lists

Nodes joined by references, what that makes cheap, and the pointer discipline it demands.

Stacks & Queues

Two ordering disciplines, and the monotonic stack that follows from one of them.

Recursion

Solving a problem in terms of a smaller version of itself, and knowing when to stop.