## Introduction - Intro to Algorithms

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Hi and welcome back to unit4 of CS215.
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We call this unit putting things in order or who is your 17th best friend.
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So, by now, you might not be surprised that I actually have a magic trick worked out
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that is, actually, in this case relevant to the topic at hand.
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So, in this magic trick, I'm going to put a bunch of animals in order with your help.
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So, here's some data, I have it stored as a Python structure at the moment.
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We caught animals--it has 11 animals in it, alphabetized dog to sparrow,
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and I've gone on the Internet and looked up the speed, how fast each of these animals is;
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it's weight, approximately in kg;
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Life span, how long they tend to live, and how big their brains are, measured in g.
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I did not go and measured these animals' brains.
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So, pretty common operation in social network analysis and lots of other problems
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is to be able to put items in order.
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So, in this particular case, we have a bunch of animals, we like to put them in order,
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but there's lots of different dimensions on which to order them.
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What we're going to do is we're going look at a linear combination of these numeric features,
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and you're going to pick from me the weight, the positive weights,
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to put on each of these different attributes and then we're going to take a sum,
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in fact, I got the code right here for you to look at.
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What I'd like you to do is run this code on this data and what you do is you call importance rank
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on this data set animals and you give it the weights.
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I gave a weight of 1 for the speed, 0.4 for the weight,
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2 for the life span, and 0.1 for the brain mass.
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So, if you would run it with this weights, it would actually compute a score for each of the animals
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and then print them out in sorted order, but I want you to give your own weight.
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Don't use mine because that wouldn't be very tricky with it.
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Any weight you want just as long as they are not negative or zero.
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But the program is going to print out are the numbers 0 through 10 for the 11 different animals
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and I want you to make a note of, I don't know, let's say the fourth highest in the list,
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the one that's associated with the number 3,
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and I want you to make note of which animal appears in this position
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and mark the corresponding circle.
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And what makes this as a magic trick is that the algorithm that I'm using, the running time is so fast,
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that it's Î¸(-n), that is to say I can compute the answer to this question
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I know what answer you're going to get, but now, you need to run it to make it so
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and let's see if you're right.
Cím:
Introduction - Intro to Algorithms
Leírás:

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Video Language:
English
Team:
Udacity
Projekt:
CS215 - Intro to Algorithms
Duration:
02:42
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