Category USACO

My USACO Practice Question

jasper Leave a comment

Over the past few week, I’ve been diving deep into USACO problems to sharpen my competitive programming skills, and each problem has helped me improve in a specific algorithmic area. Problems like Just Green Enough, Rectangular Pasture, No Time to Paint, and Painting Fence Post helped me understand the power of prefix sums especially for handling range queries and updates efficiently. I also worked on problems like Cow Operation, Field Day Sequence, and The Great Revegation, which introduced me to Disjoint Set Union (DSU), a technique that made it easier to track and merge connected components quickly. Graph traversal problems like Dance Moves, Searching for Soulmate, and Sequence Construction challenged me to use DFS in creative ways to simulate operations or build valid sequences. I even explored bitwise operations and interval merging in Convolute Intervals, which showed me how lower level optimizations can make a big difference. Each of these problems felt like a puzzle that required logic, strategy, and a good grasp of algorithms. As I practiced, I gained more confidence in using techniques like prefix sums, DFS, DSU, and bit manipulation not just in isolation, but as tools I can mix and match to solve complex problems. If you’re curious about how I solved them or want to follow my journey, you can check out all my code on GitHub: https://github.com/Jasper-World/USACO.

My USACO Practice question

jasper Leave a comment

Over the past few weeks, I’ve been practicing for the USACO Silver contests and solving a wide variety of problems that have helped me grow as a competitive programmer. Through these problems, I’ve learned several important algorithms and techniques, including prefix sums, DFS, BFS, reverse and multi source BFS, flood fill, greedy algorithms, and the two pointer technique.

One important lesson I’ve discovered while solving USACO problems is that it’s crucial not to jump straight into coding after reading the problem. If your initial idea or algorithmic concept is wrong, you might end up wasting a lot of time debugging or rewriting your solution. Instead, it’s better to analyze the constraints, for example, looking at the values of N and T to determine whether the problem can be solved with brute force, a two pointer approach, or if it requires a more optimized or mathematical solution.

Among the problems I’ve solved, one that I found challenging and both fun was “Multiplayer Moo.” The difficult part of this problem was finding the largest connected region consisting of two distinct numbers. A brute force approach that checks all possible pairs would be far too slow possibly N^2. The key insight is to only consider numbers that are adjacent to each other in the grid. By doing this, you can efficiently check which regions are connected. It’s also important to maintain an auxiliary array to keep track of visited cells or connected components that have already been processed.
https://github.com/Jasper-World/USACO

Passing USACO bronze section

jasper Leave a comment

Two months ago, I participated in the USA Computing Olympiad (USACO) Bronze division, and the result was a great success. I scored 767 points across three problems. In the first problem, Roundabout Rounding, I solved all 13 test cases correctly, and it took me about an hour to complete. For the second problem, Farmer John’s Cheese Block, I managed to pass 7 out of 16 test cases. Looking back, I believe I could have done better, but considering I hadn’t yet learned how to work with 3D grids at the time, I’m still proud and a bit surprised by how much I was able to accomplish. The last problem, It’s Mooin’ Time, was, in my opinion, the most challenging of the three, but I still managed to figure out the solution and pass all the test cases correctly.

Overall, I was very proud of myself for passing USACO Bronze. I’m now currently working toward passing Silver, and I quickly realized that Silver is much harder than Bronze. It requires a stronger grasp of algorithms and greater control over functions. Back when I was preparing for Bronze, I mostly used brute force and vectors. But now, I’ve learned more advanced algorithms such as the two pointer technique, greedy strategies, prefix sums, binary search, BFS, and DFS. On the functions side, I’ve become familiar with built in tools like sort, pair, void, abs, min, max, and more. Hopefully, by the end of this year, I’ll successfully pass Silver and begin my journey toward USACO Gold.