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‫Welcome back.

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‫Before we get started with anything else, I have a little challenge for you, and that is to take this

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‫for loop here.

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‫This nested for loop and adjust it so that our console right here or this for loop in general will not

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‫print out all elements of our matrix, but only the ones that are odd numbers.

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‫So only the two to 4 to 6 and the eight.

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‫So please adjust the code so that it does it.

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‫And just a little hint you will need to use if statements as well as the modulo operator.

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‫Okay.

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‫So I hope you passed the video and you tried it for yourself to get this running and to make the code

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‫do exactly as we like it to do.

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‫And what we all need is an if statement the checks the matrix at the i j position for modulo two because

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‫if something is modulo two zero, then it is going to be an even number.

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‫So what this basically does is it compares if the modulo remainder when you divide something by two

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‫is going to be zero.

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‫So if the remainder is zero, then we know we have an even number.

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‫Okay, so basically that's going to be it.

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‫So if this is the case, then print the number and otherwise else.

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‫We could also add a statement here where it's just console, right?

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‫Like soul and just an empty space, nothing more.

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‫Okay.

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‫So this will now print it out.

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‫And print specifically the even numbers two, four, six, eight.

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‫So that's what I meant with.

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‫We all need an F statement as well as a modulo operator.

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‫So this is the modulo operator and it works with remainders.

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‫Now, by the way, if one is the result here, so if the remainder is one, then we know that we have

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‫an odd number.

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‫So let's run it again.

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‫And you see, we only get the odd numbers from our matrix.

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‫So this was just a little challenge for you to get the juices flowing.

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‫So now let's look at how we can print the diagonal elements of a matrix.

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‫So one, five and nine, for example.

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‫Or seven, five and three.

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‫Or the other way around, actually.

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‫Three, five, seven.

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‫So how can we actually achieve that?

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‫So if we look at our nested for loop that we created here, then we realize that here I is zero and

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‫J is zero.

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‫If we look at I and J at this case, I is one and J is one, and in this case I is two and J is two.

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‫So if we want to have a diagonal, we know that I and J have to be the same.

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‫So at least for this diagonal here, four one, five and nine, four, seven, five and three, it's

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‫going to be a different story.

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‫But for the one five at nine, we can basically do something very simple, and that is to just check

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‫if the matrix.

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‫Well, actually a challenge for you.

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‫Try.

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‫Try it for yourself.

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‫Okay.

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‫So I hope you checked it.

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‫So what?

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‫We need to check this.

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‫Is I equal J.

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‫And if that's the case, then print out the value.

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‫Otherwise, print out an empty space.

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‫So let's run that real quick.

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‫And we will see that we get one, five and nine.

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‫I now I want this to look a little better.

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‫What we actually also can do is we can use a control bright line statement with an empty space and then

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‫it would look like this.

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‫So one, five, nine for aesthetic reasons.

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‫So that's something that we can achieve here.

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‫You can, of course, create a significantly more complex logic.

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‫So what you could do is you could replace the diagonal values.

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‫Now, for example, instead of just printing them out, you could assign them.

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‫So you could assign a different value for them saying something like.

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‫All of them should be a one, for example.

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‫So that could be something that you could do.

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‫And then let's actually do the for each statement underneath it.

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‫Let's run this again.

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‫And you will see that now it will be one, two, three, four, one, six, seven, eight, one.

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‫Okay, so basically replaced this five and this nine with a one.

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‫So now this is just an example of how you can do it using a nested for loop.

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‫The thing is, you can actually do it using just one for loop.

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‫It's a little easier, of course, and a little challenge for you.

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‫Try to do it with just one for loop.

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‫Okay.

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‫So basically it's just going to be this here.

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‫So we just use this for loop where it goes through the matrix get length, so through the column length,

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‫so to speak and it just prints out I.

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‫So basically saying one or in this case, zero zero.

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‫In this case one one.

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‫In this case, two, two.

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‫So this will be the position of the numbers that I just showed you.

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‫Okay.

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‫If we run this, we should also get one, five, nine.

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‫Let's look at it and we can see we get 159.

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‫Okay, now what if we want to get three, five and seven?

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‫So now I would like you to pause the video and find a logic that will print out three, five, seven

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‫instead.

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‫Okay.

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‫This will be a little more complicated because we now need to think where we need to start our eye and

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‫where we need to start.

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‫RJ Because basically what we need to do is our eye still starts at the beginning and goes up by one.

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‫So we go through one row at a time.

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‫But RJ.

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‫He's going to go down from the maximum value in this case from two.

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‫Okay.

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‫So.

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‫Okay.

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‫So and now I would like to show you a little trick how you can go down or basically show the diagonal

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‫signal from the other way around.

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‫So from three, five and seven, and therefore you can use something where a four loop is going to be.

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‫Having to counter variables.

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‫So usually let's look at a for loop.

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‫We can just enter four and then press tab twice.

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‫This is how a four loop usually looks like.

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‫Right?

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‫So you have a counter variable ie and then you have the length and in our case the length will be predefined

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‫is three because we will hardcoded this time.

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‫We know that we will just have three lines here.

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‫Of course you could also say matrix get length like so matrix get length.

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‫For the zeroth dimension.

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‫And now what you also can do, by the way, is you can add a comma here and say that J should start

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‫as two and then you decrement J.

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‫For each iteration.

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‫Like so.

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‫So now what we have is we have to counter variables.

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‫So we have the eye counter available and at the same time the j count the variable, but we are only

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‫limiting based on the eye value.

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‫So this will only work properly for a matrix that has the same amount of columns as it has amount of

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‫rows, because otherwise you would have to use a nested for loop as we've done before.

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‫So this will not work and we can just go ahead and write the matrix position I and J to our console.

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‫So let's look at it and we can see it shows three, five and seven.

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‫So this time it went from top right to bottom left.

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‫But this is just an example of what you can do with a follow up.

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‫This is not very common practice, so be careful when you use it.

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‫This is a little more difficult to read and this is also something that you should consider when developing.

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‫So if you use it in a simple example, it's going to be probably fine.

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‫But if the example becomes more complex, then this can become quite confusing, or it could potentially

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‫become quite confusing when double checking your application, or when a third developer or a second

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‫developer comes in and checks your code.

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‫So always take that into consideration when writing your code.

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‫Make it as straightforward as possible so that it stays readable.