Have you ever tried to do a brainteaser in which you have to connect the dots to make the outline of a house in one continuous stroke without going back over your lines? Or perhaps you've clicked on ...

Have you ever tried to do the brainteaser below, where you have to connect the dots to make the outline of a house in one continuous stroke without going back over your lines? Or perhaps you've ...

Let G be a graph and k a natural number. A k-coloring of G is a map c that maps the vertices of G into the set {1, 2, ..., k} (whose elements are called colors) such that no two adjacent vertices are ...