When the number of cases of an event is difficult to count directly, it is solved by dividing it into smaller and simpler counts problem partitioning. When the partial events are exclusive, they simply add up, but even if they do not, the inclusion-division principle can be used if the common part can be found.

image

relevance - binomial coefficient - Moebius transform - perfect permutation


This page is auto-translated from /nishio/包除原理 using DeepL. If you looks something interesting but the auto-translated English is not good enough to understand it, feel free to let me know at @nishio_en. I’m very happy to spread my thought to non-Japanese readers.