AP Computer Science 1.1 Review of the Basics

AP Computer Science: Review of the Basics Drill 1, Problem 1. What does this piece of code output?

AP Computer ScienceReview of the Basics
Computer ScienceAP Computer Science
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Standard Operations and AlgorithmsSearching
Test PrepAP Computer Science

Transcript

00:29

Pretty simple Request We just have to prove to the

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test and to ourselves that we know how to read

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java code and figure out what it does Well it's

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Not merely a pest problem This kind of thing is

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done all the time when debugging program right but also

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comes up quite a bit when software engineers have to

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maintain or update pulled code Occasionally you'll have to work

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with stuff that had been written five or ten years

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ago or more perhaps by someone who is no longer

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on the project and maybe they didn't leave comments in

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the code so it's tough to figure out exactly what

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it was meant to do or they thought they were

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being really cute and they left their comments and cling

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on Well good luck with that Anyway in this case

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is just eight lines but we can already see that

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there are a couple of loops that end up doing

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an awful lot in that short space So let's go

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through and decode this baby step by step All right

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up top line one sets us up with manager i

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with a value of five Go ahead and write that

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down somewhere Scratch paper in your arms whatever we want

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to keep track of where this variable takes us Line

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two initiates a wild loop which will run as long

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as an injured eye remains greater than zero so it's

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five now and so it looks like we're good to

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go Line three homeboy line three starts another loop nested

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inside the first one and this time it's A four

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loop Well four loops have three parameters The first being

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the initialization imager J is one which is what we'll

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be using is the eatery So write that on your

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arm or whatever too The second is the termination parameter

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When this condition is false the loop will no longer

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run Yes j No longer being less than or equal

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to I will stop the looting The third parameter is

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called the increments and living up to its name It'll

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increments j by one Each time the loop cycles Line

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four is inside the loop It friends the product of

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three times j and its base and he'll do it

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over and over and over over within this loop until

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j is no longer less than or equal to ay

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well first time it runs Jay is one so we

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print the product of three times one in a space

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Then it'll increase j by one and a loop will

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run again so next time it'll be three times too

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and a space and then three times three and space

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and three times for anna's face and three times five

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in space And now jay six which is greater than

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i look at your arms eyes five at the moment

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That's the necessary condition for our four loop determining through

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the chapel So now we move on to what happens

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after the four loop which is an empty print line

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statement that'll give us a new line and we subtract

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one from i you all right But we're not done

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The wild loop is still running And this time i

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is for the interior Four loop is going to run

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again and again until j is greater than i So

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jay starts over at once and we'll print three times

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one into space and three times do in the states

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hand three times three spaces and three times for in

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space but now has five which is greater than i

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So we stopped the loop here and continue on with

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an empty print line statement and decreasing i yet again

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So from here we can totally tell what these loops

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are doing and predict what will happen next The lupul

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print three six nine and stop it because i will

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be three And the local run again printing three six

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and three At that point the wild loop will cease

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running because i will no longer be greater than zero

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Got all that and it looks like the result matches

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up with the answer E and yeah that's our answer

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and here's your smoke do sure brought to you by 00:04:37.173 --> [endTime] loops Wait not again Allright we're good out No