A USAAIO Prep

Past-problem archive

Real walkthroughs of public IOAI and USAAIO problems — one per category. Each page covers the official statement, what the problem is really testing, a runnable baseline, the techniques that historically moved scores, submission gotchas, and a follow-up drill. Treat these as the canonical reference for "what a contest problem actually feels like" before you sit a mock.

How to use this page. Work through one problem per week after you've finished the stratum pages (Math → Python → ML → DL → Transformers). For each: read the restatement, attempt the baseline yourself before reading section 4, then implement at least one improvement from section 5 and measure the actual delta on your Colab notebook.

Walkthroughs ready · 4 problems

Stage B done: my own paraphrased problem brief + solution sketch + code. Click any card to open. External source links below.

CV · IOAI 2025

Chicken counting via density estimation

Build the density-map decoder on top of a provided VGG-style feature extractor; predict per-pixel bird density and integrate. CSRNet-style back-end, count-aware loss, hflip TTA. IOAI 2025 Day 1.

Open walkthrough →
 Theory · USA-NA-AIO 2025 R1 P1

Linear recurrence & complexity

Compute terms of a Fibonacci-style recurrence. Derive closed form via the characteristic polynomial. Implement O(log n) matrix exponentiation with modular arithmetic. USA-NA-AIO 2025 Round 1 Problem 1.

Open walkthrough →
 NLP · IOAI 2024 Scientific

Ciphered-language classifier

Fine-tune a tiny BERT from scratch on a deliberately unintelligible corpus, then extend it with a prototype classifier when the on-site task adds 2 unseen classes. IOAI 2024 Scientific at-home, NLP.

Open walkthrough →
 Tabular ML · NOAI China 2024 P1

Basketball shooting percentage

Predict made/missed shots from court coordinates. Polar features beat the MLP; gradient boosting beats both; knowledge distillation lets you submit the required PyTorch model. NOAI China 2024 / APOAI 2025 mock.

Open walkthrough →

External sources: IOAI-official/IOAI-2025 · forum.beaver-edge.ai · ioai-official.org · jaredliw/ioai-tsp-2025

Forum-archived contest sets

Status. Problem statements live on the Beaver-Edge AI Olympiads forum as images (forum users have flagged the accessibility gap). The index below is link-only — open the forum thread for the official statement, then write your own walkthrough page as you sit each problem. Stage B (this site's own paraphrased brief + solution sketch per problem) is in progress.

USAAIO 2026 Round 1 · 9 problems

Just released. No walkthroughs yet — link-only.

  1. Problem 1 — supervised learning, F1, UMAP basics. forum →
  2. Problem 2. forum →
  3. Problem 3. forum →
  4. Problem 4. forum →
  5. Problem 5. forum →
  6. Problem 6. forum →
  7. Problem 7. forum →
  8. Problem 8. forum →
  9. Problem 9. forum →

USAAIO 2025 Round 2 · 3 problems

Problem 3 (CLIP, 20 parts) is the most extensive single problem in the 2025 cycle.

  1. Problem 1 — 12-part theory + ML pipeline. forum (all parts) →
  2. Problem 2 — 14-part. forum (all parts) →
  3. Problem 3 — CLIP multimodal, flickr30k image-text alignment, 20 parts. forum (category) →

USAAIO 2025 Round 1 · 5 problems

Problem 1 (linear recurrence) has a full walkthrough on this site — see recurrence walkthrough. Problems 2–5 link-only.

  1. Problem 1 — Linear recurrence & matrix exponentiation. walkthrough → · forum sample →
  2. Problem 2 — 13-part affine NN / EDA pipeline. forum (all parts) →
  3. Problem 3 — 18-part. forum (all parts) →
  4. Problem 4. forum (category) →
  5. Problem 5. forum (category) →

IAIO 2024 · 6 problems

IAIO (International Artificial Intelligence Olympiad — Russia-led; distinct from UNESCO-backed IOAI). 22 sub-question threads on the forum.

  1. Question 1 — parts 1.1, 1.2. 1.1 → · 1.2 →
  2. Question 2 — parts 2.1–2.7. all 7 parts →
  3. Question 3 — parts 3.1–3.3. all 3 parts →
  4. Question 4 — parts 4.1, 4.2. 4.1 → · 4.2 →
  5. Question 5 — parts 5.1–5.4. all 4 parts →
  6. Problem 6 — parts 6.1–6.3. 6.1 → · 6.2 → · 6.3 →

Known gaps (no forum archive)

Push next. Public problems hosted elsewhere (GitHub, Kaggle, IOAI official site) without a Beaver-Edge forum mirror. Write a walkthrough page as you sit each one.

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