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DSA, Beginner

Start with complexity analysis and the JavaScript toolkit, then what every pattern is built from: arrays, prefix sums, hashing, two pointers, sliding window, binary search, recursion, sorting, stacks and linked lists.

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Complexity analysis

30 min read · 7 exercises

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  1. Complexity analysisThe one skill every interviewer is silently scoring, whether they say so or not.
    30 min read7 exercises
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    7 exercises
  2. The JavaScript toolkit for DSAA correct algorithm can still fail in JavaScript: a slow shift, a sort that puts 10 before 2, a product that loses digits, a stack that runs out. This is the reference for all of it.
    42 min read16 exercises
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    16 exercises
  3. Arrays & stringsThe two data structures every other pattern is built on top of.
    31 min read32 exercises
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    32 exercises
  4. Prefix sums and difference arraysStore the running total once, and a whole family of range questions becomes one subtraction.
    34 min read21 exercises
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    21 exercises
  5. HashingThe single most common way an O(n²) brute force becomes O(n).
    20 min read20 exercises
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    20 exercises
  6. Two pointersOne pass, two positions — how an O(n²) search collapses to O(n).
    29 min read25 exercises
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    25 exercises
  7. Sliding windowStop re-scanning the same elements — slide the window instead.
    22 min read19 exercises
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    19 exercises
  8. Binary searchHalving the search space is the single highest-leverage trick in DSA.
    27 min read24 exercises
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    24 exercises
  9. Basic recursionTrees, backtracking, DP and divide-and-conquer are all recursion wearing a costume.
    30 min read13 exercises
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    13 exercises
  10. Sorting algorithmsYou'll rarely hand-write one, but you'll constantly need to reason about them.
    36 min read15 exercises
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    15 exercises
  11. Stacks & queuesTwo rules for order, and half of interview problems secretly need one of them.
    21 min read16 exercises
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    16 exercises
  12. Linked listsNo index math, no shifting cost — the tradeoff array questions can't make.
    41 min read29 exercises
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    29 exercises

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