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Hello. Welcome back to the challenge 3 solution for section 19.

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I'm in the section 19 workspace in the challenge_3_solution project.

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And this is the project where we try to find the word matches

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in the Romeo and Juliet play.

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So let me go over my solution, and I wrote a simple function

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to help me with the solution. And we'll talk about the function in just a second.

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But let's just go through the solution at the beginning here. Here's my main

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I've got my input file stream right here called infile.

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Here's the word that I want to find. That's what the user is going to give us.

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Here's the word that I've read. So each time I loop through that file,

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I'm going to read a word. And then I've got the word count and match count,

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which are just counters that we're going to increase when we see a word

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and when we see a matching word.

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Okay. So that's it. That's the preamble there.

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And here's the good old recipe that we always adhere to, right.

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I want to open the file Romeo and Juliet. If it's not open,

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I display an error, and I leave.

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So let's get to the part of the program that's doing all the work here.

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So right here on line 29, I'm asking the user to enter the substring to search for,

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suppose they enter love.

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I'm reading that in from standard input.

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And then I'm in my loop here. So while I want to read a word

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from infile.

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Okay. So I'm going to stop at any white space. I'm using the extraction operator here.

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So I'm going to read a word into word read.

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And if it didn't fail and if it didn't give me an end file,

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I've got a word. So I'm going to increment the word count because I've seen a word.

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And then I'm going to call a function,

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which I'm going to show you in a minute that I wrote called find substring.

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And the idea here is I send into this function

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the word that I want to find and the word that was read from the file.

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And if this word happens to be a substring in that word,

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it's going to return true. When it returns true, I increment the match count.

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If it doesn't return true, i don't increment the match count.

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And I just simply go back up and loop again.

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That's it. Pretty straightforward.

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When I'm done with the loop, I've hit the end of file.

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I simply display how many words were searched,

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and how many times my matching word was found.

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Okay. That's it. So let's talk about that find substring function now,

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which I wrote up here.

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And here it is. This function, as I said, expects

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two parameters, two strings, and they're both const refs.

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In this case, what's the word to find.

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Okay. The word to find is what the user gave us love,

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which is being passed into this. And what's the target.

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The target is the word that we just read from the file,so maybe we read the word lovely

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or we read the word Romeo

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or whatever word we read.

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So what we're going to do is we're going to use the find method

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in the string class,

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which says hey target, which is this guy

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find that substring word to find within you

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and give me back the index of where you found it.

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I really don't care about the index. I just want to -- I just want to know if it was there or not.

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So if it returns std string no position,

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that means that it was not in the word, and I returned false. Otherwise, I returned true.

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Like I said, I really don't care what position it's in. I just want to know whether

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the substring exists in that target or not. That's it.

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Really, really simple. Let's run this.

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And let's search for -- again let's search for Romeo.

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I said search for Juliet this time.

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Juliet, 49 times we found the word Juliet.

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All right. That's it. Now suppose we're trying to debug this along the way. We really want to see what

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word was actually read from the file.

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So what we could do here or even better let's just see the words that match.

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We know the words that match, right, in this if statement right here, right. That's why we're incrementing match count

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So what we could do is right in here we could stay std count.

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And we could display the word that we just matched, right,

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which was the word that we read. So we could display word read

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followed by a space and no new lines that way it'll just display them one after the other.

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So let's try running this again now.

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And let's look for the word love.

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There we go. Those are all the matches that we found.

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Lovers, love, love with a question mark, punctuation,

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love performing you can see here love song,

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dear loved. There you go. So it gives us a pretty good

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gauge as to the correctness of our program.

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Obviously, we would have to do some real testing.

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And absolutely, know ahead of time how many times this word exists.

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Let's try it again with a capital l

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would love four times.

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Okay. So there you go.

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And let's see how about Romeo.

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You can see Romeo was found 132 times,

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and it was found with a period at the end,

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a period at the end again at the end of the sentence with question marks,

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Romeo's with an apostrophe. So that's it.

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That's the solution. If you came up with another solution,

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if you figured out a way to do it by reading a whole line

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of time and then splitting up the straight the words out of the line,

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that's a lot more work. But if you did that you, think it's cool,

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post it out there, so we can all learn from one another.

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All right. So I hope you enjoyed this challenge.

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In the next video, we'll learn about output streams and writing to files.