https://atcoder.jp/contests/jsc2019-qual/tasks/jsc2019_qual_f Before explaining the solution, we first explain the four typical problems. These often appears in various counting problems. Problem 1 How many are there N non-negative integer…

https://atcoder.jp/contests/jsc2019-qual/tasks/jsc2019_qual_eWe should calculate not the maximum spanning forest but the maximum pseudo forest. K - 種類数 β uses similar property. We know we can swap edges in any tree, and we can also swap…

https://atcoder.jp/contests/jsc2019-qual/tasks/jsc2019_qual_cLooking at elements from left to right, we'll decide to open or close an interval. We can determine which operation we should do by the parity of the number of intervals currentl…