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Description:
AP Computer Science 3.1 Standard Algorithms. What is the output of Recurse(3)?
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
Full Transcript
- 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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