## Abstract

Consider a directed rooted tree T=(V,E) of maximal degree d representing a collection V of web pages connected via a set E of links all reachable from a source home page, represented by the root of T. Each leaf web page carries a weight representative of the frequency with which it is visited. By adding hotlinks, shortcuts from a node to one of its descendents, we are interested in minimizing the expected number of steps needed to visit the leaf pages from the home page. We give an O(N^{2}) time algorithm for assigning hotlinks so that the expected number of steps to reach the leaves from the root of the tree is at most H(p)/(log(d+1)-(d/(d+1))logd)+(d+1)/d, where H(p) is the entropy of the probability (frequency) distribution p=〈p_{1},p _{2},⋯,p_{N}〉 on the N leaves of the given tree, i.e., p_{i} is the weight on the ith leaf. The best known lower bound for this problem is H(p)/log(d+1). We also show how to adapt our algorithm to complete trees of a given degree d and in this case we prove it is optimal, asymptotically in d.

Original language | English (US) |
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Pages (from-to) | 121-128 |

Number of pages | 8 |

Journal | Information Processing Letters |

Volume | 90 |

Issue number | 3 |

DOIs | |

State | Published - May 16 2004 |

## All Science Journal Classification (ASJC) codes

- Theoretical Computer Science
- Signal Processing
- Information Systems
- Computer Science Applications

## Keywords

- Algorithms
- Hotlink
- Probability distribution
- Tree
- Web