Dataset of 4-regular multigraphs for the second Hamiltonian decomposition problem

Each file contains 100 regular multigraphs constructed as unions of Hamiltonian cycles of different nature: *.txt – unions of random permutations generated by the Fisher-Yates shuffle algorithm; *pyr.txt – unions of pyramidal tours with only one peak; *_4peaks.txt – unions of Hamiltonian cycles with exactly four peaks. A vertex is called a peak in a cycle if its successor and predecessor have lower numbers. Hamiltonian cycles are encoded as vertex permutations. The resulting union multigraphs can be considered both undirected and directed.