This algorithm adds an attribute to each node that specifies the k-core that node belongs to. The k-core a node belongs to is the last k-core it would be part of before being removed from the graph in the next k-core. To find a k-core, recursively remove every node with fewer than k edges connected to it.
A k-core is a part of a graph with strong structure. K-cores have been analyzed for their properties, as indicators of the structure of the graph, and to help visualize graphs.
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