 The idea of the algorithm is based on the concept of contraction of an edge formula_1 in an undirected graph formula_2.Informally speaking, the contraction of an edge merges the nodes formula_3 and formula_4 into one, reducing the total number of nodes of the graph by one.All other edges connecting either formula_3 or formula_4 are "reattached" to the merged node, effectively producing a multigraph.