- #1

Xavier Labouze

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- TL;DR Summary
- Given A, a set (note P(A) its powerset) and A1, A2... Ak, k subsets of A. What is the cardinality of P(A1)∪P(A2)∪...∪P(Ak) ?

**Mentor note**: In this thread I (Mark44) have edited "cardinal" to "cardinality." In English, we talk about the "cardinality of a set," not the "cardinal of the set."

Given A a set of n elements - note |A| its cardinal and P(A) its powerset. Let A

_{1}, A

_{2}... A

_{k}, be k subsets (not empty) of A.

**What is the cardinality of P(A**- Is there a formula or a rapid algorithm to compute it ? (I don't see how to compute it in polynomial time when the subsets are not pairwise disjoint...)

_{1})∪P(A_{2})∪...∪P(A_{k}) ?Thank you.

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