Bunch of aproximated graph edit distance algorithms.
[1] Upper bound of order O((n_1+n_2)^3)
[2] Lower bound of order O(n_1*n_2)
[1] Riesen, Kaspar, and Horst Bunke. "Approximate graph edit distance computation by means of bipartite graph matching." Image and Vision computing 27.7 (2009): 950-959.
[2] Fischer, Andreas, et al. "Approximation of graph edit distance based on Hausdorff matching." Pattern recognition 48.2 (2015): 331-343.