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Today I wanna talk about a nice problem that I solved on CSES known as Critical Cities. Summarizing, given a directed graph and a pair of source and target vertices, your task is to find out all vertices which belong to every path between them. [Read More]

Today I wanna talk about a great mathematical theorem known as Lucas’ Theorem that is used in combinatorics problems. To illustrate it, I’ll show a problem that I solved from Beecrowd, the problem in this case is called Sibi-Xor. Summarizing, you have to find the sum of the XOR of... [Read More]

Today I wanna talk about a nice problem from “Latin America Regional Contests 2019” called Algorithm Teaching where you have to find the largest set containing smaller sets that are, for any two sets, incomparable. The core of the problem is to arrange the algorithms taught by a teacher in... [Read More]

Today I’ll talk about a standard C++ data structure that is amazing: the bitsets. They can handle binary operations such as left shift («), right shift (»), and (&), or (|), and xor (^), and they can have a fixed number of bits. Now you may ask me which types... [Read More]

There is a class of graphs called Perfect Graphs for which some problems can be solved in polynomial time, such as: maximum clique, maximum independent set, and coloring. One such graph is the Split Graph, which can be checked by a simple $O(|V| \log |V|)$ algorithm, by simply checking if... [Read More]