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Welcome back, I hope you had
fun doing that challenge.

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I'm in the Section 20 workspace
and the challenge 3 - Solution.

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This is an example of explaining
something is going to be much

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easier than explaining the
actual problem to begin with.

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This code is so simple.

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Hopefully, did it similar
to the way I did it.

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Let the STL do its thing.

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The STL is super powerful.

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Let's take a look at part one.

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Here's the solution for part one.

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And let's walk through
this one line at a time.

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We've got our map here called
words, and it's a map of

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string, integer key value pairs.

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I've got a line that's what I'm going
to read the line from a file into.

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I've got a word and this is how
I'm going to process my words.

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Here's my file.

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My file is words.txt.

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If I can't open it, I'm down here.

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And I'm out.

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If I can open it then what I want
to do is I want to process the

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words from the line I just read.

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And that's not so easy to do
there, it's much easier to do

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if you use a string stream.

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And if you look at the I O
videos I talked about string

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streams in that video.

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So, in this case, I'm creating a
string stream called ss over line.

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So, remember we just read a line,
let's say we read, and this is a test.

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And we don't want to
deal with new lines.

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We don't want to deal with any of that.

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So, we just read that line.

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And then what we're going to
do is we're going to create the

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string stream from that line.

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So, that's going to put in that buffer.

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So, now I can read words
from the string-stream and it

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makes it really, really, easy.

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So, you can see right there
while I'm going to extract a

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word from the string-stream.

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So, I'm going to extract this
word, and then this word, and then

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this word, and then this word.

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For each one of those words, I'm
going to pass it into clean-string.

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So, I can get rid of
the periods at the end.

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And suppose I have something
like commas and so forth.

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It'll get rid of that.

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So, in this case, I will end up with
a clean word and all I have to do

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is just say words, that's my map.

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I'm using the subscript operator
right, so in this case it's

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equivalent to saying something
like this, words, this.

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Let's assume that we're working
with that guy right there.

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That is my key if it doesn't
exist, the value is going to

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be added with the key, right.

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So, in this case, that's my key.

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What do I want to do?

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I want to increment the value
at that key, simple as that.

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So, now I just put that word in once.

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The next time I see that same
word, it will already be there.

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So, it's going to increment
this to 2 and so forth.

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That's it, that's the code.

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It's really one line right there
that does all the good work.

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I commented this line out right here.

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And you can use that for debugging
purposes if you'd like to make

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sure that you're reading these
lines correctly from the file.

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That's it, that's part one.

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I told you it's pretty simple.

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I'm closing the file and then I'm
calling display words and display

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words will come up here for part one.

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And it's going to call
this function right there.

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And all it's doing is it's
just doing a lot of formatting

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which is just to look nice.

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But for each pair from the
words map, I'm dealing with

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the first and the second.

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The first is the key.

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The second is the value.

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So, this is just displaying
Aunt 8, Frank 3 and so forth.

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Okay, let's look at part two.

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Here's part two.

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Very, very, similar the idea.

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We've got our map is words, and
this is a little bit different

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right because I've got a key here.

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And my value is not an Int.

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In this case, it's a set OF Ints.

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The whole point of this
exercise was to show you how

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you can build these things up.

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I mean it's really, really, powerful.

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Many times, we need to
solve a problem like this.

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And you'll see some programmers
creating classes for words, and

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for lines, and you create a new
class that's going to model the

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occurrences of a line you really
don't need to do any of that

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because the STL does this for you.

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This is a real powerful concept.

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I mean I'm already modeling key value
pairs right here, why do I need to

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create another class to do this when
I just need to solve this problem.

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Okay, so in this case, I've
got the same variables.

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I've got the same file.

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I'm opening my file
right here on line 88.

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I need to have a running count of line
numbers because I need my line number.

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So, I'm just starting
line numbers at zero.

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I mean I haven't really
read anything yet.

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Now what I'm going to do is I'm going
to read, let me clear this a little bit,

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I'm going to read the line
into this variable from the file.

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And now I want to increment line
number because I just read a line.

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So, my number now would be 1.

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Again, I'm using the string-stream just
to process words, cleaning the string,

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and this is the only difference here.

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So, now I'm doing something like words,
again let's assume we're using that

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same that word we just read this.

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This piece right here, that's the key.

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This will return the pair and I
can access the value right there.

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So, what am I doing?

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I'm inserting line number into
the value which is that guy.

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Right! So, I'm using the sets insert method
which is really, really, easy.

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The first time through the line
number is the line number, I'm

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just inserting that key value pair.

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The next time it's just
updating that value.

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And that's it, let's
run this one last time.

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Here's my output.

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And you can double check it in
the code light editor but it's

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really, really, straightforward.

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Here's part one where you've got
your word and the number of times

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it occurs, and down here is part
two where we've got the word and the

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line numbers that it occurred on.

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Okay, so, hopefully, you
had fun with this one.

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And hopefully, you can
see how easy it is now.

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So, in the next video we'll talk
about the container adapters,

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stack and queue, and we'll have
another challenge for those.