USACO 2022 US Open — full contest set
← All past problems · Official 2022 US Open results
The US Open closes the 2021–22 USACO season — 5 hours per division, three problems each across Bronze, Silver, Gold, and Platinum. Strong performance here (combined with the earlier Dec / Jan / Feb rounds) determines invitations to the summer training camp where the four-student IOI team is selected. This page is my landing for all 12 problems.
Round at a glance
| Field | Value |
|---|---|
| Contest window | Late March 2022, 4-day window |
| Duration | 5 hours, individual, open-book within the contest window |
| Divisions | Bronze, Silver, Gold, Platinum |
| Problems per division | 3 (12 total) |
| Scoring | Out of 1000 per division; partial credit via subtasks (Silver+) |
| Significance | Final round of the 2021–22 season; the season's top US scorers earn an invitation to summer camp where the IOI team is chosen |
| Allowed languages | C++17, Java, Python 3 (C++ strongly preferred at Gold/Platinum) |
| Notable problems | Platinum P1 "262144 Revisited" is a callback to the 2016 March "262144" problem — same merge rule, but now answer every contiguous subarray |
Divisions
Bronze · greedy, search, recipes
Photoshoot · Counting Liars · Alchmey. Even-prefix reversals on a G/H string, minimum statements to ignore for consistency, and a recursive recipe-feasibility problem on a DAG of metals.
Silver · topology, strings, parity
Visits · Subset Equality · COW Operations. Greedy on a functional graph (max acyclic subset), per-letter-pair precomputation for fast subset queries, and an XOR-of-counts invariant for COW reduction.
Gold · greedy + DP + tree
Apple Catching · Pair Programming · Balancing a Tree. Sweep with a priority queue for time–space matching, interleave-counting DP modulo a prime, and a tree DP with interval bounds on each node.
Platinum · DP, games, LIS
262144 Revisited · Hoof and Brain · Up Down Subsequence. O(N · max) doubling DP on the classic 2048-style merge, attractor analysis on a directed game graph, and a longest "U/D-pattern" subsequence in O(N √N log N) with Hunt–Szymanski-flavor BITs.
How I'm using this set
- Bronze and Silver: real timed 60–90 min attempts, full implementation, then editorial comparison.
- Gold: read the statement and constraint, brainstorm an approach for 20 min before peeking at the key idea.
- Platinum: study problems — read editorial, sketch the data structure, then reimplement from memory the next day.
- Spot-compare with the 2016 March "262144" so the doubling DP feels familiar before opening the Revisited variant.