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All right guys, it's time for yet another coding challenge.

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And this coding challenge is going to put into use what you've learned about

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while loops,

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while also testing some of the previous knowledge you got on functions.

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So I want you to head back to Reeborg's World and change to hurdle number 3.

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And take a look at the premise for this particular race.

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Right?

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Essentially what's happened this time is that the wall placement has become

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random. So let's say we restart this game, you can see that in this case,

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there's a wall here, one here, one here, one here. There's four in total.

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But if we try a different version,

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then you can see that there is different wall placement each time.

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Not only don't we know where the wall is going to be,

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we also don't know how many walls there will be.

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So code such as what we did before using a for loop

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telling our robot to jump six times is not going to work.

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And instead, we're going to have to use the conditions

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whether if front is clear or whether if there's a wall in front or whether

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if we're at the goal and also their negations,

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so not front is clear, not wall in front,

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not at goal. See if you can use what you've learned about while loops

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as well as your previous knowledge on if statements and functions to complete

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this challenge. When you have written the correct code,

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no matter what kind of wall situation or hurdle setup they have,

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it should always be able to get to the goal.

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And while I've been looking at this challenge, I know there is a very,

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very simple way of bypassing this challenge,

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which is simply to get the robots go up here and all the way down here,

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going past all the hurdles.

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But that's not the point of the challenge. In order to complete this challenge,

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you must get your robot to follow the path that set out in the dotted lines

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instead of bypassing it and doing something completely different

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just to get to the final goal. Pause the video, have a think about this,

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have a read of the world info popup here,

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and then think about how you can solve this challenge. So give it a go now.

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Right?

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All right. So essentially, if we don't know where the walls are going to be,

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then we have to test to see if there is a wall in front,

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or if there is no wall in front.

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And if there is a wall in front, then we're going to jump.

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But if there's no wall in front, then we're just going to move forwards.

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And we're going to do this and test this for as long as we're not at the goal.

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So we're going to need a while loop

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that's very similar to our previous while loop that I showed you in the demo. While

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we're not at goal or rather while

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this particular condition is not true,

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then we're going to repeat and loop some lines of code.

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The first thing we're going to do is we're going to use an if statement to check

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whether if there is a wall in front.

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So I'm going to say, if wall in front,

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if this is true,

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then I'm going to perform the jump function and get it to jump over the wall.

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But if there is no wall in front, so namely else,

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well, in this case, we're simply just going to move forwards.

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And because our jump function is always going to get us to face the right way,

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which is this direction here towards the goal,

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then this move forward by one function is always going to take us in this

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direction.

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So let's take a look at this code and let's step through it step by step.

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So the first thing we're going to check is are we at the goal. At_goal is going

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to be false. So not false is going to be true.

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So while this condition is true,

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we're going to carry out all the lines of code inside.

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So that means we should jump into this if statement and check

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is there a wall in front? So at this point,

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this should be false because there is nothing in front.

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So it should bypass the if statement and it should go to the else statement.

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In which case it should move forward by one step. So that's the end of one loop

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and we go back to the beginning: are we at the goal yet? Nope, we are not.

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But now when we run into our if statement,

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this check should now come up as true,

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because there is a wall right in front of our robot. So in this case,

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it's going to go into the if statement and perform the jump function. 

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Now our jump function that we defined previously actually gets us to move

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forward by one step first,

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before we actually hurdle over this wall. So in this case,

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if we try to do the same thing,

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then it's actually going to hit our robot into a wall.

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We have to modify our jump function by removing this first move function.

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So instead we get it to just turn left, go up, turn right,

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go right, turn right, go down and then turn left to face the right direction.

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This is a pure hurdle without that extra step in the beginning.

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And instead we're going to only move if there is no wall in front.

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So we've changed the code.

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Let's back it up and try this again with a different setup.

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And in this case, you can see as my code is going through the different steps,

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it's checking to see if there's a wall in front. If there is,

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then it's going to jump over it. If there isn't,

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it's just going to move forward by one step and then it's going to reevaluate.

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So this way, once it gets to here,

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it's actually going to reevaluate the while loop quite a few times

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and every time it's going to be the else statement that fires.

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It's going to move, move, move, move, move until it hits a wall again

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and then it's going to jump over and take us to the finishing line.

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Did you manage to get this correct? Did you manage to get the solution right?

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If not be sure to review the previous lessons on the while loop so that you

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familiarize yourself with it

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and also if you got stuck on changing the jump function,

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then be sure to remember that whenever you get stuck,

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it's important to test your assumptions. And in this case,

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you could have pressed the step-through button many times to see which line of

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code is being triggered at which point,

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and which is the moment where our code actually fails

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so you can figure it out and fix it.

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Now on the next lesson, I've got yet another code challenge for you.

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So head over there and give it a go.