Inclusion-Exclusion Principle
Version 1.0.0 · Updated 2026-07-30
CORE DEFINITION
When calculating the union of multiple sets: first add the sizes of each set, then subtract the sizes of pairwise intersections, then add the sizes of triple intersections... alternately adding and subtracting to avoid double counting. Scaffold role: count without duplication or omission. Systematically handle overlapping parts in categorical counting to avoid overcounting or undercounting.
SCAFFOLDING EFFECT
Reduce cognitive load
Count without duplication or omission. Systematically handle overlapping parts in categorical counting to avoid overcounting or undercounting.
Anchor fast decisions
The size of the union of multiple sets requires alternately adding and subtracting intersections to correct for double counting: |A∪B| = |A| + |B| - |A∩B|, and for three sets add back the triple intersection. The essence is to systematically handle overlapping parts to achieve counting without duplication or omission.
MINIMUM ACTION
In progress 0/5Practice this model in one real situation:
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Source support: Explicit
- zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E6%8E%92%E5%AE%B9%E5%8E%9F%E7%90%86verified
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