Discrete Maths, Lecture-13 : Counting-III

These are my notes from 13th lecture of discrete mathematics course taught at Arsdigita university by Shai Simonson. Other posts relating to this are here.

This lecture covers following topics..
1. Inclusion-Exclusion principle (a generalization of sum rule using same theorem from set theory)
2. Pigeonhole Principle
3. Derrangement Problem

Here are my notes...