U USACO Prep

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

Every USACO round is 4 divisions × 3 problems = 12 problems total. This page indexes the February 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. The whole contest revolves around three recurring scenarios — Milk Pails, Circular Barn, and Load Balancing / Fenced In — each escalating in difficulty as you move up divisions.

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 February 2016 results page on usaco.org: usaco.org/index.php?page=feb16results. Each problem links to its official statement (statements live at usaco.org/index.php?page=viewproblem2&cpid=…, cpids 615–626).

Round metadata

ContestUSACO 2016 February
Window4-day window in February 2016, 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)
Recurring scenariosMilk Pails, Circular Barn, Load Balancing / Fenced In — each appears in 2–3 divisions with escalating constraints.
ScoringIOI-style partial credit, 1000 points per problem, 3000 max per division
Allowed languagesC, C++11, Java, Python 2.7, Python 3
Promotion cutoffsSet per-contest by USACO; check the results page for exact thresholds.

The contest at a glance

Bronze

Bronze · 3 problems

1. Milk Pails — fill an M-pail from two smaller pails X, Y without overflowing; maximize total.

2. Circular Barn — pick one exterior door of a ring barn to minimize total clockwise walking distance for cows.

3. Load Balancing — place two axis-aligned fences to minimize the max number of cows in any quadrant (N ≤ 100).

Open Bronze write-up →
 Silver

Silver · 3 problems

1. Circular Barn — each cow's energy is the square of doors walked; assign cows to rooms to minimize total energy.

2. Load Balancing — same fence-placement problem as Bronze P3 but with N ≤ 1000 and coords ≤ 106.

3. Milk Pails — BFS on (x, y) states with at most K operations; minimize |target − (x+y)|.

Open Silver write-up →
 Gold

Gold · 3 problems

1. Circular Barn — N ≤ 105 version of the squared-energy assignment; rotate-and-greedy with prefix sums.

2. Circular Barn Revisited — choose k ≤ 7 doors to unlock on a ring; DP over which doors are open.

3. Fenced In — MST on a grid with (n+1)(m+1) cells where edge weights are gap widths; sort gaps and use a Kruskal-style count.

Open Gold write-up →
 Platinum

Platinum · 3 problems

1. Load Balancing — N ≤ 105 version with coordinate compression + BIT to binary-search the optimum split.

2. Fenced In — same MST as Gold but n, m ≤ 25,000; avoid materializing the (n+1)(m+1) edges and use the sorted-gap count formula directly.

3. Circular Barn — k ≤ 7 doors with n ≤ 1000 and ri ≤ 106; DP over rotations × subsets-of-arcs.

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. February 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.