Graphs and coloring
Colors, subgraphs, labels and paths that visit every vertex.
20 problemsCollections
Selected problems that share a subject or a research tradition. Each leads to its own overview and sources.
Within Combinatorics · All collections
Geometric extremes
Packing, covering, distances and other limits set by geometry.
11 problemsBases and transversals
Rearranging bases, choosing distinct symbols and listing minimal hitting sets.
4 problemsGames and strategies
Perfect play in chess, winners in graph games, and pursuit strategies.
3 problems