22. Counting Using Principle of Inclusion-Exclusion
The lecture discusses the principle of inclusion-exclusion, explaining its definition and applications in counting problems. It elaborates on how this principle can be extended to find the cardinality of the union of multiple sets and provides a proof of concept through examples. Additionally, it presents an alternate form of inclusion-exclusion useful for counting specific types of elements, followed by multiple real-world applications and exercises to illustrate the concepts more clearly.
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Sections
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What we have learnt
- The principle of inclusion-exclusion helps to accurately count the cardinality of unions of sets while avoiding over-counting.
- The formula can be generalized for any number of sets, ensuring all overlaps are considered.
- The alternate form of inclusion-exclusion aids in counting elements lacking specific properties.
Key Concepts
- -- Principle of InclusionExclusion
- A counting technique that provides a way to compute the size of the union of multiple sets by appropriately adding and subtracting the sizes of intersections.
- -- Cardinality
- The number of elements in a set, often represented by the symbol |A|.
- -- Derangements
- A permutation of a set in which none of the objects appear in their original positions.
- -- Combinatorial Functions
- Functions that describe how to select elements from sets and count combinations.
Additional Learning Materials
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