U USACO Prep

USACO 2016 December — the whole contest, all four divisions.

Every USACO round is 4 divisions × 3 problems = 12 problems total. This page indexes the December 2016 round end-to-end: Bronze through Platinum, with the official statement link, the key idea, complexity target, and a runnable C++ reference for each problem on the per-division pages.

Bronze (all 3) → Silver (all 3) → Gold (all 3) → Platinum (all 3) →
Authoritative source. All problem titles, constraints, and results below are taken from the official December 2016 results page on usaco.org: usaco.org/index.php?page=dec16results. Each problem links to its official statement (statements live at usaco.org/index.php?page=viewproblem2&cpid=…, cpids 663–674).

Round metadata

ContestUSACO 2016 December
WindowDec 16–19, 2016 (4-day window, single 4-hour personal timer)
Length per division4 hours (Dec/Jan/Feb format; US Open is the 5-hour round)
Problems per division3
Total problems12 (Bronze 1–3, Silver 1–3, Gold 1–3, Platinum 1–3)
ScoringIOI-style partial credit, 1000 points per problem, 3000 max per division
Allowed languagesC, C++11, Java, Python 2.7, Python 3 (C++11 was the default at the time)
Promotion cutoffsSet per-contest by USACO; check the results page for exact thresholds.

The contest at a glance

Bronze

Bronze · 3 problems

1. Square Pasture — find the smallest axis-aligned square containing two given non-overlapping rectangles.

2. Block Game — minimum number of letter blocks across N two-sided spelling boards (per-letter max).

3. The Cow-Signal — scale an M×N character grid by K in both dimensions.

Open Bronze write-up →
 Silver

Silver · 3 problems

1. Counting Haybales — Q interval-count queries over N sorted positions (binary search).

2. Cities and States — count special city pairs whose first-two-letters / state-code interlock (hash counting).

3. Moocast — directional walkie-talkie reachability; for each source, max cows reachable (BFS, N ≤ 200).

Open Silver write-up →
 Gold

Gold · 3 problems

1. Moocast — minimum squared transmission radius that keeps every cow connected (MST / binary-search-on-edge).

2. Cow Checklist — interleave two ordered cow lists from H1 to HH, minimizing sum of squared step distances (DP).

3. Lasers and Mirrors — minimum 90° mirror placements to route the beam from source to barn (BFS on rows/cols).

Open Gold write-up →
 Platinum

Platinum · 3 problems

1. Lots of Triangles — for each v, count triangles formed by N ≤ 300 trees containing exactly v interior trees.

2. Team Building — count pairs of size-K subsets where FJ's i-th ranked cow beats FP's i-th, mod 109+9 (2D DP).

3. Robotic Cow Herd — sum of K smallest distinct configurations across N locations (heap on differences).

Open Platinum write-up →

How to use this set

  1. Pick your division. Open the full division page and read the three statements before writing any code.
  2. Solve P1 first, P2 if time, P3 only if you're cruising. December problem 1s are usually the cheapest points.
  3. Time-box. 4 hours total. Don't spend more than ~90 minutes on a single problem without a working subtask submission.
  4. Compare to the reference C++. Each problem on the division page has a ~30–50 line reference solution. If yours is much longer, ask why.
  5. Verify with the editorial. Official editorials are linked from each problem page on usaco.org.