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Unformatted text preview: Algorithms in the Real World (15853), Fall 09 Assignment #3 Due: 15 October 09 You are not permitted to look at solutions of previous year assignments. You can work together in groups, but all solutions have to be written up individually. Problem 1: Suffix Trees (10pt) Consider a suffix tree build over a text string S of length n . Describe how to augment Suffix trees to support each of the following types of queries. 1. FindBefore(P,e) : find a string P in S starting at any position before e , if one exists. This should run in O (  P  ) time and the space for the augmented data should be O ( n ). I briefly described this in class. 2. FindClosest(P,s,e) : find the string P in S that starts before s . If P appears multiple times before s , it must return the closest one to s . This should run in O (  P  log n ) time and the space for the augmented data should be at most O ( n 2 ). If you can reduce the time or space, you can get extra credit (if described concisely and clearly). Notethe time or space, you can get extra credit (if described concisely and clearly)....
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 Fall '09
 GuyBlelloch
 Algorithms, Hamming Code, Error detection and correction, Polynomial code, LDPC Codes, Galois Field GF, augmented data

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