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Today I’ll talk about a problem from Beecrowd called Flea Circus. I solved this problem using a Treap (I recommend reading this article), and the implementation is very straightforward if you are already familiar with the data structure. [Read More]

There is a useful optimization trick involving DP on trees that I would like to discuss. It was detailed in the comments of this Codeforces blog. In short, you can define a DP over the vertices of a tree and compute its value for each $v$-subtree by combining the children... [Read More]

There is a great problem on Kattis called It’s a Mod, Mod, Mod, Mod World with a short statement: given $p$, $q$, and $n$, find $\sum_{i = 1}^{n} \left[ (pi) \bmod q \right]$. [Read More]

Today I’ll show the randomized solution for the problem E. Game of the Year. To solve it, I used XOR hashing. [Read More]

Today I’ll show the solution to the problem Dating (you can solve this problem on other platforms, such as Codeforces, too). The problem asks you to count the number of pairs of different types with the same number along a specific simple path in a tree. [Read More]