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Edexcel D1 - 17th June, 2016 [Exam discussion]

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Original post by target21859
Someone asked this before but it wasn't answered. Is there an equation for the maximum number of passes for a bubble sort?


Maximum number of passes is n-1, because in the worst case scenario, every item is in the wrong place (list is reversed) so every item will have to be moved to the correct place. Once you've done n-1 passes, the last item is already in the correct place so it's n-1 instead of n.

I've attached a June 2015 IAL question where they asked for the maximum number of passes.


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Original post by farrl005
Can anyone help me with question 8 b on the june 2014 D1 paper?? I have no idea what to do haha

https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/June%202014%20QP%20-%20D1%20Edexcel.pdf


The gradient of the objective line must be between the gradient of AB and CD.
Original post by NotNotBatman
The gradient of the objective line must be between the gradient of AB and CD.


Why
Original post by Pablo Picasso
Why


Hard to explain, but it's because if the objective lines gradient is equal to the gradient of BA, then it will pass through the points A and B at the same time, same with CD. If it was a little bit less than grad of BA then the objective line would cross B first, so in order for it to cross A first ( so that A is the minimum) grad of F > grad of BA where F is the objective line. It would be the same with CD, but less than.
Original post by NotNotBatman
The gradient of the objective line must be between the gradient of AB and CD.


ah thank you! :smile:
Original post by farrl005
ah thank you! :smile:


But use the gradient BA instead of AB, as they should be calculated all going in the same direction, but I can't edit my post for some reason.
I hate D1 so much it's so boring :frown:((((((( good luck for friday everyone!
Got this straight after M2 on Friday.

As a helpful note, it would be worth knowing the definitions for the exam (just learn them on Friday morning or something). They come up every other year and didn't last year, so a question would be very likely.
Here because of my momonumental cock up of M3 and FP2, this is a nice break in comparison.
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kennz
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Has Slack ever come up in an exam? Or the triangle inequality?
@NotNotBatman
(edited 7 years ago)
How do you find the objective function to draw the objective line on the Jan 15 IAL paper please? Question 6(d)

https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/January%202015%20(IAL)%20QP%20-%20D1%20Edexcel.pdf
(edited 7 years ago)
When on a dijkstras problem and it asks you to find the shorted round via another node, what's the best way to work out the answer to this?

I've just been using trial and error :colondollar:
Original post by Katiee224
When on a dijkstras problem and it asks you to find the shorted round via another node, what's the best way to work out the answer to this?

I've just been using trial and error :colondollar:

Do you have a specific question? You usually have to use a different final value for the last node in order to work backwards
Original post by Katiee224
When on a dijkstras problem and it asks you to find the shorted round via another node, what's the best way to work out the answer to this?

I've just been using trial and error :colondollar:


Original post by Glavien
How do you find the objective function to draw the objective line on the Jan 15 IAL paper please? Question 6(d)

https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/January%202015%20(IAL)%20QP%20-%20D1%20Edexcel.pdf


Original post by NotNotBatman
But use the gradient BA instead of AB, as they should be calculated all going in the same direction, but I can't edit my post for some reason.


What's the hardest paper you guys have done?
Original post by Katiee224
When on a dijkstras problem and it asks you to find the shorted round via another node, what's the best way to work out the answer to this?

I've just been using trial and error :colondollar:


So you want the shortest route from A to G via D. Take your final value at D (since that's the shortest route to D) and just work from there. It's usually very simple and if not just do some calculations on paper
How long does a D1 paper normally take you?
And if they ask you for the reason for using dummies, how do you word it, assuming it's not the dependacy reason?
Original post by techfan42
What's the hardest paper you guys have done?

I'd say do the International papers if you're looking for the hardest.
Original post by Glavien
How do you find the objective function to draw the objective line on the Jan 15 IAL paper please? Question 6(d)

https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/January%202015%20(IAL)%20QP%20-%20D1%20Edexcel.pdf


Let P = ax+3ay for any value of a. (a is the cost)

Original post by Katiee224
When on a dijkstras problem and it asks you to find the shorted round via another node, what's the best way to work out the answer to this?

I've just been using trial and error :colondollar:


You could use the working values. If that doesn't work, say you needed to find the shortest from s to t via f. Find the shortest from f to t, then the shortest from s to f.
Original post by Pablo Picasso
How long does a D1 paper normally take you?
And if they ask you for the reason for using dummies, how do you word it, assuming it's not the dependacy reason?


2 hours lol I'm f***ed

Dummy enables unique representation of activities in terms of their end events
Original post by Student403
So you want the shortest route from A to G via D. Take your final value at D (since that's the shortest route to D) and just work from there. It's usually very simple and if not just do some calculations on paper


will bare that in mind, cheers

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