*This post is part of a series that considers what can be learned from the problems in each chapter of uHunt, a tool for competitive programming practice. You can find the rest of the posts in the series by visiting my uHunt post category.*

I recently finished the last of the 37 starred problems in uHunt Chapter 2. I’m solving these problems as part of a learning project that I’m calling Project 462, after the 462 uHunt starred problems.

Chapter 2 highlights problems that require more specific data structures than the ad-hoc problems in Chapter 1. The chapter starts out with arrays, covers familiar data structures like stacks and queues, and ends with problems that use Segment Trees and Fenwick Trees, data structures that you may not have heard about in college.

The uHunt approach is to categorize problems by the algorithm, data structure or technique that the authors recommend using to solve them. In addition to the category, each problem has a level — generally 1 through 4 — indicating its difficulty level. The Chapter 2 problems mostly use the same range of levels as the Chapter 1 problems. But for each Chapter 2 problem, there is an extra step of learning or reviewing the appropriate data structure. Although they start with a data structure recommendation, most Chapter 2 problems still require problem-solving techniques and creative thinking.

In many competitive programming situations, you won’t know which data structure to use in advance. The goal of the uHunt style of practice is to get familiar with the range of problems that you’ll come across, so that you know which data structure, algorithm, or technique to use when you see a similar problem in the future.