Must the hypercube be Euler?

Not necessarily. A hypercube graph is not necessarily an Euler graph. Euler graph refers to a graph with one or more paths, so that all vertices on each path are traversed exactly once. Hypercube graph is a special graph, which consists of n nodes and n edges, each edge connects two nodes, and each node has adjacent nodes. Hypercube graphs are connected graphs, but not all hypercube graphs are Euler graphs. To judge whether a hypercube graph is an Euler graph, it is necessary to check whether there is a path that passes through all vertices and the path is closed. If such a path exists, then a hypercube graph is an Euler graph; Otherwise, it's not Otto. The hypercube graph is not necessarily an Euler graph, but should be judged according to the specific situation.