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Standard Algorithms Videos 19 videos

AP Computer Science 2.1 Standard Algorithms
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APCS: Standard Algorithms Drill 2, Problem 1. How much slower is InefficientSum than EfficientSum in the best case for an array of n elements?

AP Computer Science 2.5 Standard Algorithms
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In this computer science drill question, figure out which implementation will copy one array over to another.

AP Computer Science 3.3 Standard Algorithms
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AP Computer Science: Standard Algorithms Drill 3, Problem 3. What should go in "expression 1" to satisfy the conditional statement?

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AP Computer Science 3.1 Standard Algorithms 176 Views


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Description:

AP Computer Science 3.1 Standard Algorithms. What is the output of Recurse(3)?

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Transcript

00:00

Sorry And here's your smoked use your brought to you

00:05

by rijker zhan brought to you by rekers jin Brought

00:09

to you by rekers asian brought to you by consider

00:14

the following code segment What is the output of re

00:17

curse three Ah we're thinking all right And here the

00:22

mental answers on numbers Okay this question Assessing what we

00:28

know about rikers in which is essentially having a method

00:31

call itself This creates a type of loop that goes

00:34

round and round around until some condition typically called the

00:37

base case is satisfied like a dog chasing its tail

00:40

in telling finally catches it a simple implementation of riker

00:43

shin might look something like this All right well this

00:47

method would take an imager And if it's greater than

00:50

zero print hello plus the imager Then it will decrease

00:54

the imager by one and call itself again And if

00:58

it's still greater than zero it'll do it again can

01:00

again and again it'll rikers decreasing over and over and

01:05

saying hello annie in inger goes up there until it

01:08

reaches zero go at zero it will simply return the

01:11

zero and the method will no longer call itself it's

01:15

a bit like the recursive algorithm shown in this question

01:17

except this one is also doing some funky math to

01:20

the imager so we'll need to carefully plot out what's

01:22

happening step by step here's our sniffing and the question

01:26

is asking pre output of re curse free All right

01:30

well starting at the top we're getting our method ready

01:32

with the parameter into end which will let us accept

01:35

that three and play with it as variable end when

01:38

rikers three gets called if it is less than one

01:42

will return the number one doesn't apply to us at

01:44

the moment though else will return one plus the product

01:48

of three times re curse and minus one better known

01:51

as to wait a min We're trying to calculate what

01:55

happens in rikers right now How can we use something

01:58

that hasn't been calculated yet Has a factor in our

02:01

calculation Shouldn't they shatter the universe somehow Well we're just

02:05

gonna have to dive into the first method again and

02:07

see how deep the rabbit hole goes at this point

02:09

Imager and is currently three and we're being asked for

02:12

re curse and minus one so it's just like calling

02:16

re cursed too We did The fancy man if end

02:20

now to remember is less than one return One else

02:24

return one plus three times rikers and minus one So

02:29

we'll be calling recruits again this time as reversed one

02:32

so it ends less than one return One else returned

02:35

one plus three times were cursed and minus one and

02:38

calling rikers yet again this time as rikers Zero Ah

02:42

but here we go If and is less than one

02:45

which it is We return one The product of rikers

02:48

zero is one We've stopped the lute e Now we

02:53

just have to climb back out of this home were

02:54

in back to rikers one We now know that riker

02:57

zero equals one So occurs one equals one plus the

03:01

product of three times one well in california three times

03:04

One two three and add one to that for four

03:07

So recruits one equals four and climbing up a rung

03:10

refers to it three times for his twelve plus one

03:14

is thirteen to rikers to is thirteen And at rikers

03:18

three three times thirteen is thirty nine plus one which

03:21

is forty So the product of rikers three is forty

03:24

Who A lot of work Someone really should write a 00:03:26.9 --> [endTime] computer program to handle it for us next time

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