TL;DR: The ECO method as discussed by the authors enumerates some classes of combinatorial objects by means of an operator that performs a "local expansion" on the objects, and uses these constructions to deduce some new funtional equations verified by classes' generating functions.
Abstract: In this Paper, we illustrate a method (called the ECO method) for enumerating some classes of combinatorial objects. The basic idea of this method is the following: by means of an operator that performs a "local expansion" on the objects, we give some recursive constructions of these classes. We use these constructions to deduce some new funtional equations verified by classes' generating functions. By solving the functional equations, we enumerate the combinatorial objects according to various parameters. We show some applications of the method referring to some classical combinatorial objects, such as: trees, paths, polyminoes and permutations
TL;DR: The goal of this paper is to survey the state-of-the-art in packing and decomposition of combinatorial objects such as graphs, digraphs, and hypergraphs by smaller objects.
TL;DR: A necessary and sufficient condition for the regularity of rank 3 combinatorial maps is given in terms of Coxeter groups, and the difficulty in classifying the regular maps on surfaces is revealed.
TL;DR: In this article, the authors describe recent advances in the study of random analogues of combinatorial theorems, and present a collection of examples of such analogues, including the following:
Abstract: We describe recent advances in the study of random analogues of combinatorial theorems.