Five new lessons
New chapters on time complexity from constraints, modular arithmetic, complete search, sorting with comparators, and tree DP.
What changed
These chapters came from comparing the Learn map with the topics USACO Guide covers. Each has the full lesson format, a runnable exercise and judge practice.
Time complexity from constraints: read the input size and time limit, then pick an approach that fits.
Modular arithmetic and fast power: keep large counts in range and raise numbers to big powers quickly.
Complete search: try every option when the input is small enough.
Sorting, comparators and selection: sort by your own rule, then sweep through the result in order.
General trees and tree DP: walk trees with any number of children and combine answers from the leaves up.
Try it
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