 Enumerative combinatorics

Enumerative combinatorics is a branch of combinatorics concerned with the counting of structures that satisfy specific criteria. It involves the enumeration of combinatorial objects, such as permutations, combinations, graphs, and more, often under various constraints. The main goals of enumerative combinatorics include: 1. **Counting Objects**: Finding the number of ways to arrange or combine objects according to given rules. For example, how many ways can we arrange a set of books on a shelf?