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Data structures and algorithms, explained with pictures

Short, friendly lessons with real-world pictures and step-by-step diagrams. Then solve original interview problems right here in Python or JavaScript, with hints one step at a time.

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Start here · 3 min readTopic 1: Arrays and hashing

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Topics

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  1. 1Arrays and hashingLearn arrays and hash maps for coding interviews with pictures: what each operation costs, plus counting, 'seen before' and prefix sum patterns.3 min5-question quiz3 problems
  2. 2Two pointers and sliding windowTwo pointers and sliding window explained with pictures: when each works, step-by-step diagrams, a quiz and practice problems in Python and JavaScript.3 min5-question quiz3 problems
  3. 3Stacks and queuesStacks and queues explained with pictures: push, pop, bracket matching and the monotonic stack pattern, with a quiz and practice problems.2 min5-question quiz3 problems
  4. 4Linked listsLinked lists explained with pictures: pointer rewiring, dummy heads and fast and slow pointers, with step-by-step diagrams and practice problems.2 min5-question quiz3 problems
  5. 5TreesBinary trees and BSTs explained with pictures: DFS, BFS, recursion and the BST rule, with step-by-step diagrams, a quiz and practice problems.3 min5-question quiz3 problems
  6. 6GraphsGraphs explained with pictures: BFS, DFS, grids, cycle detection, topological sort and Dijkstra, with diagrams, a quiz and practice problems.3 min5-question quiz3 problems
  7. 7Binary search and sortingBinary search without off-by-one bugs, explained with pictures: the template, rotated arrays, binary search on the answer and sorting costs.3 min5-question quiz3 problems
  8. 8Dynamic programmingDynamic programming explained with pictures: find the state, write the recurrence, memoisation vs tables. With a quiz and practice problems.2 min5-question quiz3 problems

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