75 how do we determine a good ordering approach 1 move

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Unformatted text preview: the items in the list • Example: List of four students S1, S2, S3, S4 Probability of retrieval: S1 ß། 5% S2 ß། 15% S3 ß། 30% S4 ß། 50% Texp = 1* 5/100 + 2*15/100 + 3*30/100 + 4*50/100 = 3.25 Reverse the list à༎ Texp = 1* 50/100 + 2*30/100 + 3*15/100 + 4*5/100 = 1.75 How do we determine a good ordering Approach 1: (“move forward”) - Maintain a count with each item, initially 0 - Update count when item is retrieved July 2nd, 2013 - allow the retrieved item to ‘move forward’ if its count warrants pros: - data is in optimal order eventually à༎ takes time cons: - takes more memory to store count Example: Suppose incidents are as follows: S3, S2, S3, S4, S4, S4,...
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This note was uploaded on 02/04/2014 for the course CS 234 taught by Professor Baranoski during the Spring '09 term at Waterloo.

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