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Rebuild Your Problem-Solving

A guided path through coding practice problems, organized by the pattern each one teaches and ordered to rebuild real problem-solving fluency — whether you're starting out or shaking off rust from leaning on AI. Pick a stage and start. The hard problems carry a "test out" note if you already know the material.

Stage 0 — Warm-Up: Shake the Rust Off

Not patterns — just easy wins. Prove to yourself you can take a problem from description to a working, accepted solution. Seniors: do one or two and move on.

  • Warm Up (coming soon)

Stage 1 — Foundations: Linear Patterns

The highest-leverage patterns, and the ones hiding inside almost everything later.

  • Frequency Counter — The moment you catch yourself about to write a loop inside a loop — comparing every item against every other item — stop. A frequency counter does the same job in a single pass by remembering what you've already seen. You spend a little memory to buy a lot of speed.
  • Two Pointers (coming soon)
  • Sliding Window (coming soon)
  • Prefix Sum (coming soon)

Stage 2 — Sorting & Searching

  • Binary Search (coming soon)
  • Merge Intervals (coming soon)

Stage 3 — Linked Lists

  • Fast Slow Pointers (coming soon)
  • In Place Reversal (coming soon)

Stage 4 — Stacks & Queues

  • Stack Matching (coming soon)
  • Monotonic Stack (coming soon)

Stage 5 — Recursion & Trees

  • Recursion Fundamentals (coming soon)
  • Tree Dfs (coming soon)
  • Tree Bfs (coming soon)

Stage 6 — Heaps & Top-K

  • Top K Elements (coming soon)
  • Two Heaps (coming soon)

Stage 7 — Backtracking

  • Subsets (coming soon)
  • Permutations (coming soon)

Stage 8 — Dynamic Programming

The most-atrophied skill for returning devs — so it gets real depth, and it's built last.

  • Dp 1D (coming soon)
  • Dp 2D (coming soon)
  • Dp Knapsack (coming soon)
  • Dp Sequence (coming soon)
  • Dp Palindrome (coming soon)

Stage 9 — Graphs

  • Graph Traversal (coming soon)
  • Topological Sort (coming soon)

Stage 10 — Optional Extensions

Add these once the core is stable; each appeared in only one or two of the research passes.

  • Greedy (coming soon)
  • Bit Manipulation (coming soon)
  • Union Find (coming soon)
  • Dijkstra (coming soon)
  • Tries (coming soon)
  • Cyclic Sort (coming soon)