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Hello, everyone. Welcome back.

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This is the solution to
the section 11 challenge.

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And I'm in the section 11 workspace
and the challenge solution project.

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I'd like to go over one possible
solution to this project.

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This is a solution that
I've done, very modular, 

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all the functions are there.

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they're all small,

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they do one thing,
and they do them well.

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So let's go through this.

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Let's look at our main first.

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Let's start there.

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Main defines numbers, which
is the vector of integers,

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just like we've had before.

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And it's got a character variable
called selection, that's where

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the user is going to type in their
selection, their menu selection.

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Now we've got our do loop.

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Our do loop, now there's -- I've
folded the code here.

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There's obviously more code here
in the switch statement, but

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I'm just going to show you the
overall structure of this loop.

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So here we're doing
do display the menu.

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Notice that now we're calling
a function to display the menu.

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Then I'm going to get the
selection from the user.

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So whatever they type in, I'm
going to store in selection.

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But I'm not just going to store it in
selection, I want to make it uppercase

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and then store it in selection.

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That way I don't have to check
for lowercase and uppercase every

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time I check for a selection.

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And I want to do this loop
while the selection is not

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equal to an uppercase q.

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Okay, so that's pretty much it.

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Now let's take a look at
our display menu function.

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And it's right down here.

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And I'll expand it right now.

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And you can see that that's
the function display menu.

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And all it is is the output
statements, just like we

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had before inside the main.

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So in this case whenever I
need to display the menu, I

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can call this function and
I'm doing that exactly here.

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Okay, now let's take a look
at the get selection function.

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Here's the get selection function,
and you can see the name of

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the function is get selection.

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It expects nothing but it
does return a character.

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So in this case, I'm defining
another character variable in here.

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Remember, this variable here
is local to this function.

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I'm simply reading from the
keyboard their selection.

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And I'm converting it to
uppercase and returning it.

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Okay, so that's that one.

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So at this point, I've
displayed the menu.

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And remember, the menu has at the very
bottom of the menu, enter your choice.

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So I don't really need to prompt the
user for anything, it's already there.

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So I'm displaying the menu.

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I'm getting their selection,
and selection will now contain

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an uppercase character.

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Okay, perfect.

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So now we're going to switch
off of that character.

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And let me expand the
switch statement here.

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So in this case, if the selection
is a p, I'm going to call a

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function called handle display.

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Because remember, p is to print
out all the integers in the vector.

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And I'm going to pass in
the vector to that function.

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If it's an a, I'm going
to do a handle add.

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M is handle mean, s is
handle smallest, l is handled

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largest, q is handle quit.

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In default, I'm just going
to handle an unknown.

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So you can see now that the logic in
main is exactly like it was before

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except we're calling functions.

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We don't have all that
code written in here.

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Also this allows us to
think modularly, right.

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Now I've got functions
doing those defined tasks.

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So again, it's that boss
worker analogy at work

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here, it's perfect for that.

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Let's take a look at handle display.

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So in this case, so
the user selects p.

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Notice I don't have to check
uppercase and lowercase anymore

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because the get selection function
already made everything uppercase.

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So I'm going to call handle
display, and I'm going to

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pass in the vector to it.

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Because obviously, it needs
to display the vector.

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Let's come over here to
handle display, and you can

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see the function right here.

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Now notice handle display, it expects
a vector, and I'm passing that

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vector in by reference and const,
just as we've spoken about before.

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This handle -- this display
method really has no business

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changing that vector.

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So I'm not going to even take the
chance that it will, I'm passing it.

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By reference so, I don't
have to copy it and const.

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So let's take a look at that.

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All right, so we've
got our vector here.

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So I'm checking to see if
the size of the vector is 0.

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In which case, it's empty, and
I'm displaying the list is empty.

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Otherwise, I'm calling a
function called display the list.

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And I'm passing in that
vector, the same vector I got,

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I'm passing to the function.

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I could have looped in
here and displayed the list

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right in here of course.

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But I decided to create another
function because you know we

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could tweak the behavior of
what the display looks like.

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And I don't want all that
code in here unnecessarily.

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So let's take a look at display list.

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It's toward the bottom.

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I'm going to scroll down here.

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There's the display list
function right here.

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Again, it expects the same vector
that was sent to the function prior.

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And now if you look at the code, it's
going to print out a left bracket.

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Then it's going to loop through
that vector and print out

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each number, just like before.

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But you can see that this
list displays just the list.

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That's all it does.

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And whenever I need to display
a list of integers, I could just

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send it right into this function.

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Okay, so that's display list.

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I'll scroll back up.

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And let's talk about handle add.

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So now we're here handle
add, it's another function.

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Whenever the user presses a, they want
to add a number to the list, right.

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So I want to call handle add and I
want to pass the list, the vector.

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So let's see the handle add method.

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I'll scroll down slightly, and
we'll see handle add is right here.

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Now notice that in this case,
I'm still passing the vector

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by reference because I want to
add an integer to it, right.

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So I need to have the
reference to it but not const

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because I need to change it.

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I need to ask the user for an
integer and store it in the vector.

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So let's look for that code.

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We're doing everything right in here.

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We're saying there's an
integer called num to add.

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Remember your scope rules here that
integer is local to this function.

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I'm asking the user to enter
an integer to add to the list.

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I'm getting that integer
from them from the keyboard.

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And then I'm simply calling the
pushback method of the vector

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class with the number to add
and displaying the message.

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That's it.

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Really, really easy.

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Okay, so let me go
back up to the main.

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And let's see handle
mean, how does that work?

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Well, we'll go to the handle mean
function, which is right here.

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Again, it expects a reference
to a vector and it's constant.

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I don't want my handle
mean modifying the vector.

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So what do we do?

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We check to see if
the vector is empty.

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If it is, we just say unable to
calculate the mean the list is empty.

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Otherwise, we call calculate
mean, and we pass in the vector.

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It's going to return a
double to me which I'm going

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to display right in here.

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So it's going to say the mean
is whatever number I get back.

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All right, so let's take
a look at calculate me.

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And I'll scroll down here.

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This is calculate mean, notice
again, it's the same vector, same

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syntax here by reference constant.

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There's my total.

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I'm looping through those numbers,
adding them all up to total.

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And then I'm casting one of these to
a double and dividing by the size.

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Exactly like we had before.

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It's pretty much the same code that
we had in the prior challenge, the

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section nine challenge except we're
breaking it up into modules here.

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So that's it.

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That's calculate mean.

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And I think you can see where
we're going with the rest of this.

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Here is let me close up handle mean,
we've got handle smallest, handle

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largest work exactly the same way.

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And then handle quit and
handle unknown, we're really

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doing very little in there.

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But I decided to make them
functions because you never know

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what you need to do in there.

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I mean suppose you're working
with files and the user quits

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and you want to you know
close up files and so forth.

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I'd like to do that in a function
and not here in the main.

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I want to keep my main
really, really simple, easy

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to read and straightforward.

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So my handle quit kind
of looks like this.

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Right here, you can see handle quit,
it's all it's saying is goodbye.

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And my handle unknown is saying
unknown selection, I guess

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I should spell that right,
unknown selection try again.

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Okay, so that's pretty
much the solution.

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I've got -- let me scroll up to
the top, and I've got all the

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function prototypes at the top. So
there are my function prototypes

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here the prototypes for displaying
the menu and getting the user

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selection, display the menu
expects nothing, returns nothing.

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Git selection expects
nothing, returns a character.

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Then I've got my menu
handling function prototypes.

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Notice that all of them expect
a reference to the vector that's

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constant except handle add because
handle add needs to change the

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vector, so it can't be constant.

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Then I've got handle
quit, handle unknown.

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And then I've got the functions
that actually do the work right the

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display list, displays the list.

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Calculate mean, give me the vector, I'll give you
back the double that's the mean.

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Get smallest, same idea.

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Get larger, same idea except
we're returning an integer.

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Okay, so what do we want to do?

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Let's let's modify this
program a little bit.

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Let's add some functionality to it.

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Suppose the user wants to
see if a specific integer

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is in the list or not.

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Okay, so how do we do that?

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Well, there's a couple
of things we need to do.

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Obviously, we need to do some
function prototyping here.

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So let's do that.

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Let's put it right under
here, under handle largest.

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We'll say void, how
about just handle find?

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We're going to find an
integer in that vector, right.

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It's not going to change the
vector, but I still need the vector.

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So I'm going to say const a vector
of integers, and I want it by

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reference and we'll use the v.

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Again, we don't have to use the
parameter names in here, but

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I'm going to just use the v.

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So that's my handle find.

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Okay, now here we need to
know -- so here we need a

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function that's actually going
to do the finding, right.

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And it's going to return
a Boolean, true or false.

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I really don't want to know
how many times it's there.

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You could certainly write
a function like that.

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But let's just call it find.

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And what does it expect?

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Well, it expects that vector
to look through, right.

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And again, it's a vector of
integers, and it's by reference.

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And what else does it expect?

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Well, it expects the integer
that you're looking for.

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So in this case, let's
just call it target.

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That's the integer I'm looking for.

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So those are my prototypes.

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But before we even get to those
prototypes, let's fix up the menu so

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that it displays that - that f, right.

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So I'm going to go
down to display menu.

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And right after display largest
I'm just going to say cout.

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And we'll put an f in there,
and we'll say find a number.

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All right, so that should display now.

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Now what do we do?

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Well, we need to handle
that case in main, right.

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So we'll do it right after
the largest right here.

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So we'll say case f in this case
and we don't have to worry about

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the lower case because it's going
to be converted to an upper case.

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And we'll say handle find.

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And we've got numbers.

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All right, perfect.

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So now what we need to do is
we need to write these two

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functions that we prototype.

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We need to write handle find
and we need to write the

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find function, these two.

240
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So let's do handle find first.

241
00:11:10,560 --> 00:11:14,830
And we'll put it right at the bottom
of the handle functions, right

242
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here right after handle largest.

243
00:11:16,770 --> 00:11:18,780
And we could write a comment
in here, but I'm not going to

244
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right now just to save time.

245
00:11:20,340 --> 00:11:21,570
So there's my handle find.

246
00:11:22,559 --> 00:11:24,889
Okay, now what does the handle
find function have to do?

247
00:11:24,890 --> 00:11:28,700
Well, it has to ask the user to enter
the integer they want to find, right.

248
00:11:29,040 --> 00:11:30,620
So let's just call it target.

249
00:11:32,800 --> 00:11:34,430
And we'll initialize it to 0.

250
00:11:34,430 --> 00:11:38,910
And we'll just say something
like cout, enter the number

251
00:11:38,910 --> 00:11:43,330
to find or to search for
whatever you want to call it.

252
00:11:44,980 --> 00:11:47,540
And we'll read that into target.

253
00:11:50,400 --> 00:11:51,529
Okay, now what do we do?

254
00:11:51,540 --> 00:11:54,009
Well, we've got that function
we still need to write the find

255
00:11:54,009 --> 00:11:55,439
function that returns a Boolean.

256
00:11:55,880 --> 00:11:57,080
So we're going to use that right

257
00:11:57,080 --> 00:11:59,990
now without even writing it because
we know what it looks like. We

258
00:11:59,990 --> 00:12:01,420
wrote the prototype for it, right.

259
00:12:01,469 --> 00:12:08,310
So I'm going to say if find,
and I'm going to pass into

260
00:12:08,310 --> 00:12:10,020
it the vector and the target.

261
00:12:13,720 --> 00:12:15,529
Let me get rid of some of
those parens, that's it.

262
00:12:15,889 --> 00:12:20,130
So if find that target and
this vector returns true,

263
00:12:20,670 --> 00:12:22,130
then the integer's in there.

264
00:12:23,570 --> 00:12:30,489
So we could just write
something like target was

265
00:12:30,490 --> 00:12:37,440
found, else target wasn't found.

266
00:12:52,129 --> 00:12:54,339
And I'll put some new lines
at the end, some endlines.

267
00:12:57,630 --> 00:12:59,430
That's pretty much
handles that function.

268
00:12:59,710 --> 00:13:01,800
So what do we have left to implement?

269
00:13:02,000 --> 00:13:05,089
Well, we need to implement -- let
me scroll up a little bit here.

270
00:13:05,349 --> 00:13:07,720
We need to implement this
function, right here, the one

271
00:13:07,720 --> 00:13:09,390
that returns the true false value.

272
00:13:10,180 --> 00:13:12,360
And I'm going to put that all
the way at the bottom with all

273
00:13:12,360 --> 00:13:14,500
my other good functions that
doing that are doing work.

274
00:13:14,950 --> 00:13:16,930
Do it right after it
gets smallest right here.

275
00:13:18,380 --> 00:13:19,780
Let's write it right here.

276
00:13:20,350 --> 00:13:21,949
And there's the prototype, right.

277
00:13:22,300 --> 00:13:23,459
So what am I going to do here?

278
00:13:23,460 --> 00:13:26,139
Well, I'm going to loop
through the vector and compare

279
00:13:26,139 --> 00:13:28,380
each element to the target.

280
00:13:28,889 --> 00:13:30,169
If it's there, I'm out.

281
00:13:30,209 --> 00:13:31,970
If it's not, I keep looping.

282
00:13:31,970 --> 00:13:34,420
And if I get to the end,
I never found it, right.

283
00:13:34,640 --> 00:13:40,890
So we can do something like for,
again, auto num for each element

284
00:13:40,890 --> 00:13:42,330
through the loop will be called num.

285
00:13:42,820 --> 00:13:44,770
And there's my collection, the vector.

286
00:13:45,059 --> 00:13:50,100
And we'll just say if num is
equal to my target,

287
00:13:51,870 --> 00:13:54,470
then I'm done. I found it.

288
00:13:54,600 --> 00:13:55,710
I'm going to return true.

289
00:13:56,090 --> 00:13:58,569
Now if we get all the way to the end
of the loop, we don't want to put

290
00:13:58,570 --> 00:14:00,060
this here, you want to put this here.

291
00:14:00,389 --> 00:14:04,029
We'll just simply say
return false, right.

292
00:14:04,029 --> 00:14:04,980
We never found it.

293
00:14:05,889 --> 00:14:07,189
So let's run this.

294
00:14:09,480 --> 00:14:12,310
Okay, we've got an error that says
number was not declared in this

295
00:14:12,310 --> 00:14:15,180
scope because it should be numbers.

296
00:14:15,730 --> 00:14:18,130
All right, hopefully, you see that
error right there, which is the typo.

297
00:14:19,340 --> 00:14:22,600
And let's try it again.

298
00:14:23,459 --> 00:14:24,280
There's our run.

299
00:14:24,370 --> 00:14:25,780
Here you see the f in the menu

300
00:14:25,890 --> 00:14:28,130
now so let's find a number.

301
00:14:28,130 --> 00:14:29,210
Let's find a 100.

302
00:14:29,680 --> 00:14:31,360
Notice how it asks me
for the number to find.

303
00:14:31,360 --> 00:14:32,790
Now the list is empty, right.

304
00:14:32,790 --> 00:14:33,819
So I should not find it.

305
00:14:35,340 --> 00:14:37,140
100 was not found, goodbye.

306
00:14:37,150 --> 00:14:37,700
What happened.

307
00:14:38,429 --> 00:14:39,420
That's an error, right.

308
00:14:39,780 --> 00:14:41,359
I should have never printed goodbye.

309
00:14:41,959 --> 00:14:43,370
Let's quit and see what's going on.

310
00:14:46,270 --> 00:14:49,630
Need a break statement, that's
why we need to test our code,

311
00:14:50,240 --> 00:14:51,310
forgot the break statement.

312
00:14:51,310 --> 00:14:54,580
Remember, with the switch it goes to
the next one, so handle quit fired.

313
00:14:55,690 --> 00:14:56,890
Let's try this one more time.

314
00:14:57,819 --> 00:14:59,170
Okay, so let's find 100.

315
00:15:00,059 --> 00:15:01,310
100 was not found.

316
00:15:01,750 --> 00:15:02,579
We get the menu again.

317
00:15:03,139 --> 00:15:05,759
Let's add 100.

318
00:15:06,729 --> 00:15:09,490
And let's look for it again.
So I'm pressing f for find.

319
00:15:09,600 --> 00:15:10,710
Let's find 100.

320
00:15:11,270 --> 00:15:12,800
Now it says 100 was found.

321
00:15:13,429 --> 00:15:14,579
And let's print the numbers.

322
00:15:16,219 --> 00:15:17,219
There you go, 100.

323
00:15:17,879 --> 00:15:21,160
So we've modularized our system
into a series of functions.

324
00:15:21,710 --> 00:15:24,970
We easily added a new behavior
to this which is the find.

325
00:15:25,290 --> 00:15:29,670
And you can see now the code is
longer, for sure, because you will

326
00:15:29,670 --> 00:15:31,429
also have a lot of comments in here.

327
00:15:31,790 --> 00:15:36,140
But you've got these really
well-defined logical functions

328
00:15:36,540 --> 00:15:38,319
that are much easier to debug now.

329
00:15:38,320 --> 00:15:40,700
If there's something wrong, you
can come in here and tweak it.

330
00:15:40,940 --> 00:15:44,000
You can also extend the
behavior of the add rather

331
00:15:44,000 --> 00:15:45,640
than having just one big main.

332
00:15:45,640 --> 00:15:48,129
And if you make any changes,
you're going to put all your

333
00:15:48,130 --> 00:15:51,269
logic in there and that main
gets out of control very quickly.

334
00:15:51,620 --> 00:15:54,800
Okay, so hopefully, your solution
it's probably going to be different

335
00:15:54,800 --> 00:15:56,530
from mine, and that's perfectly fine.

336
00:15:57,090 --> 00:15:58,400
Hopefully, it worked out okay.

337
00:15:58,400 --> 00:16:01,230
And if you have any comments on it,
please leave them in the course forum.