dsa4 min read
Inclusion-Exclusion Principle: Counting with Overlaps
Apply the inclusion-exclusion principle to count elements satisfying union of conditions. Solves divisibility, coverage, and derangement problems.
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Combinatorics
2 articles
dsa3 min read
Combinatorics: nCr, Pascal's Triangle, and Catalan Numbers
Compute combinations nCr efficiently with precomputed factorials, Pascal's triangle for small n, and Catalan numbers for tree/parenthesis counting.
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