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Unformatted text preview: CS161  Introduction David Kauchak For me, great algorithms are the poetry of computation. Just like verse, they can be terse, allusive, dense and even mysterious. But once unlocked, they cast a brilliant new light on some aspect of computing. Francis Sullivan What is an algorithm? Examples sort a list of numbers find a route from one place to another (cars, packet routing, phone routing, ...) find the longest common substring between two strings add two numbers microchip wiring/design (VLSI) solving sudoku cryptography compression (file, audio, video) spell checking pagerank classify a web page ... What properties of algorithms are we interested in? does it terminate? is it correct, i.e. does it do what we think its supposed to do? what are the computational costs? what are the memory/space costs? 1 what happens to the above with different inputs? how difficult is it to implement and implement correctly? Why are we interested? Most of the algorithms/data structure we will discuss have been around for a while and are implemented. Why should we study them? For example, look at the java.util package * Hashtable * LinkedList * Stack * TreeSet * Arrays.binarySearch * Arrays.sort Know whats out there/possible/impossible Know the right algorithm to use Tools for analyzing new algorithms Tools for developing new algorithms interview questions? :) * Describe the algorithm for a depthfirst graph traversal. * Write a function f(a, b) which takes two character string arguments and returns a string containing only the characters found in both strings in the order of a. Write a version which is O( n 2 ) and one which is O( n )....
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 Summer '09
 Algorithms

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