Original subtitles

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All right guys, I've got a fun coding challenge for you today,

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and it is a problem called fizzbuzz.

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Now this is probably one of the most asked questions at interviews for

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programmers because it tests the way that you think,

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and it allows the interviewer to see how you use your logic to solve a problem.

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And the problem we're going to tackle is a children's game called

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Fizzbuzz. Last time I checked the programmatic solution was actually up on

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Wikipedia.

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So I recommend reading the Wikipedia article only after you've solved this

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Programming challenge. The rules of fizzbuzz are really simple.

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Basically, you have a bunch of kids who sit around in a circle and going

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clockwise. The first kid says 1, the second kid says 2.

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But then when a kid encounters a number that's fully divisible by three,

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then instead of saying that number, he's going to say Fizz.

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And when the number is divisible by five,

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instead of saying the number, they should say Buzz.

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And if the number is divisible by both three and five, for example, 15,

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then they should say Fizzbuzz.

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So your program is going to replicate this for all the numbers up to and

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including a hundred. To start off, it will probably look something like this.

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It's going to print one, and then on the next line

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it will print two and then fizz,

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because three is divisible by three. And then four,

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and then five is divisible by five so it's a buzz.

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And then six is fizz because it's divisible by three and so on and so forth.

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This is what your program has to do. Take a look at the instructions,

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make sure that you understand what it is that your program has to do

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and then pause the video and try to give this a go.

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All right. So the first thing we have to do is to create a range, right?

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So let's say that for number in range, and our range is between 1 and 100,

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so we have to include 101 in here.

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And what we want to do is we want to check whether if the number's divisible by

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three, divisible by five,

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or if it's divisible by both three and five.

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Now we could write our code by doing this in order, right? We could say

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if number % 3 is equal to zero,

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then it's divisible

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by three.

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So you might think that you could write the code like this,

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but there is a crucial problem in the logic here

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namely that we know that the if, elif, else statements will stop

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once it's found one statement that's true. For example,

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if we take the number to be 15,

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15 divided by three is equal to zero

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so it's going to carry out whatever instruction is inside this if statement

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and then it's going to be done with it. It's going to skip this one

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and crucially, it's going to skip this one

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which is what we really need. Instead of structuring our code like this,

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what you might have done and what you should've done is in fact,

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have this at the top.

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So first check if it's divisible by three and by five,

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and then if that is not true,

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then check to see if it's divisible by five and then divisible by three or the

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other option works as well.

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You could do it like this. Because these two have no overlap in terms of the

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results and then it doesn't really matter.

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So now we can finally write our code because we can say, well,

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if the number that we're currently encountering is divisible by both three and

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five, then we have to print Fizzbuzz.

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If it's only divisible by three, then we're going to print fizz.

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And if it's only divisible by five, then we're going to print buzz.

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All right.

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Now that still leaves the remaining numbers, right?

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Because the remaining numbers

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which don't fit any of the criteria should just be printed out as the number.

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We can catch that quite easily with an else statement that catches basically every

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other number, in which case, we're just going to print the number.

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So now, if I go ahead and run this code,

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then you can see that all the way from 1 to 100,

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it's been able to work out which ones are fizz, which ones are buzz,

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and which ones are fizzbuzz. How did you get on with it?

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If you got stuck or if you don't understand why this logic matters,

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then I want you to try both versions that I showed you and see it

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step-by-step using the Thonny program just as we did before.

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That way you can visualize what's actually happening in terms of the logic and

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how it's flowing from one step to the next, to the next. Now,

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once you've done that, then go back to your exercise and try to complete it.

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It's really, really important that you don't just say, "Oh yeah, I understand

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now." It's a really good idea to make sure that your code actually works at the

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end of the day and to write the code yourself. Today

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we've learned all about loops and we're going to apply it in our final project.

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So that's what's waiting up for you in the next lesson.

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So head over that once you're ready.