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Please select all the situations below that are POSSIBLE and do not mark those that are IMPOSSIBLE. Each list of numbers is a degree list (list of the degrees of all the vertices) of a graph. If there are extra restrictions - the graph is simple, or a tree, etc - it will be noted in the question.

a. Graph, degrees: 1, 2, 3
b. Tree, degrees: 0, 0, 1, 1, 2, 3, 3.
c. Tree, degrees: 1, 1, 1, 1, 2, 4
d. Simple graph, degrees: 1, 2, 3
e. Simple graph, degrees: 0, 0, 0, 2.

Solution Preview

Before considering each graph in turn, the two definitions we need for simple graphs and trees, we state as:

Definition: simple graph
A graph is simple when it has no loops and no two distinct edges have exactly the same pair of ends.

Definition: tree
A tree is defined as a *connected* graph that contains no simple closed paths (i.e. it has no polygons as subgraphs).

a. Graph, degrees: 1, 2, 3

This is possible by construction. (Note: there are an even ...

Solution Summary

This solution is comprised of a detailed explanation to graph appropriately.