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Cecilia Holmgren
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Svante Janson
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Matas Sileikis
Keywords:
Random trees, Fringe trees, Normal limit laws, Pólya urns, m-ary search trees, Preferential attachment trees, Protected nodes
Abstract
We study fringe subtrees of random m-ary search trees and of preferential attachment trees, by putting them in the context of generalised Pólya urns. In particular we show that for the random m-ary search trees with m≤26 and for the linear preferential attachment trees, the number of fringe subtrees that are isomorphic to an arbitrary fixed tree T converges to a normal distribution; more generally, we also prove multivariate normal distribution results for random vectors of such numbers for different fringe subtrees. Furthermore, we show that the number of protected nodes in random m-ary search trees for m≤26 has asymptotically a normal distribution.