DSA Factory
Curriculum
Level 1 · Foundations

Arrays

About 42 steps, from the first idea to a mastery test.

  1. Stage 0What an array isFree
    1. 1Positions start at 04 min
    2. 2The length tells you where things are5 min
    3. 3Changing a value in place6 min
  2. Stage 1TraversalFree
    1. 1A loop visits every box6 min
    2. 2Count what matches6 min
    3. 3Stop when you find it7 min
    4. 4Walk backwards7 min
  3. Stage 2Traversal with stateFree
    1. 1Remember the best so far7 min
    2. 2Two things at once6 min
    3. 3Carry a total forward7 min
    4. 4Compare with the previous box9 min
  4. Stage 3In-place changesFree
    1. 1Change every box where it is5 min
    2. 2Reverse in place8 min
    3. 3A write position9 min
    4. 4Remove in place8 min
  5. Stage 4RotationFree
    1. 1Rotate right by one7 min
    2. 2Rotate by k, with a copy9 min
    3. 3Rotate in place10 min
  6. Stage 5Two pointersFree
    1. 1Pair sum in a sorted array8 min
    2. 2Count pairs below a target10 min
    3. 3Squares in sorted order10 min
    4. 4Merge two sorted lists10 min
  7. Stage 6Arrays and hashingFree
    1. 1Remember where you first saw it8 min
    2. 2Remember the latest position8 min
    3. 3Only start at the start10 min
    4. 4Ask the set in order7 min
  8. Stage 7Prefix sumsFree
    1. 1Pay once, answer fast9 min
    2. 2Left side, right side8 min
    3. 3Same total twice9 min
    4. 4Count stretches that hit k10 min
  9. Stage 8Sliding windowFree
    1. 1Slide, don't re-add8 min
    2. 2Judge every window8 min
    3. 3Grow, then shrink10 min
    4. 4Keep the window valid10 min
  10. Stage 9Kadane’s algorithmFree
    1. 1Extend or start fresh10 min
    2. 2Flip the question6 min
    3. 3Around the corner10 min
    4. 4Cheapest so far8 min
  11. Stage 10MasteryFree
    1. 1Balanced bits12 min
    2. 2Best window, no repeats12 min
    3. 3Widest container12 min
    4. 4Best product12 min
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