AQA A-level Computer Science Paper 1 (3rd June 2019) Unofficial Mark Scheme Watch

RedEyeBen
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1.1) Improve the bubble sort (2marks) ; Avoid checking the last n-1 items on the nth pass through the algorithm as you know they will already be in order.
1.2)Why doesnt a sorting algorithm become intractable?; for an algorithm to be intractable it needs to have an exponential time complexity or greater. A bubble sort only has a time complexity of O(n^2) and a merge sort has O(nlogn).
1.3) how to solve an intractable problem?; use a heuristic approach, relying on your past experiences to give an estimate of a solution.
2.1) trace the turing machine; https://www.thestudentroom.co.uk/att...4&d=1559580948
2.2) ???
2.3) ???
2.4) ???
3.1) Soduku grid ; ???
3.2) ???
3.3) ??
3.4) ??
3.5) ??
3.6) ??
4.1) What does * mean ; Zero or more occurences of previous character
4.2) What does ? mean; Zero or one occurence of the previous character
4.3) Which strings are valid?; ???
Section B
5.1) ???
5.2) ???
Section C
6.0) ???
7.1) ???
7.2) ???
7.3) ???
7.4) ???
7.5) ???
7.6) ???
8.1) ???
8.2) ???
8.3) ???
8.4) ???
9.1) ???
9.2) ???
9.3) ???
9.4) ???
9.5) ???
Section D
10.1) ???
10.2) ???
11.1) ???
11.2) ???
12.1)???
12.2)??
13.1)???
13.2)???


comment any more questions/answers and ill add them to this post
Last edited by RedEyeBen; 3 months ago
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Evil Homer
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Amazing, good luck on getting this filled in!

How did you think the exam went?
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whyamialive
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2.2) What does this program do? I think i said copy paste??
2.3) What does the term universal Turing machine mean?? I said a turing machine that can simulate any other turing machine given any input.
was there a 2.4?
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BiologyBoy2019
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Question 1.2: A statement “when sorting a large list it’s said to be intractable but when the list is smaller it’s said to be tractable”

My safari elephant question solution in java:
OUTPUT - http://prntscr.com/nx3zvj

CODE - http://prntscr.com/nx40sz
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whyamialive
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(Original post by BiologyBoy2019)
Question 1.2: A statement “when sorting a large list it’s said to be intractable but when the list is smaller it’s said to be tractable”

My safari elephant question solution in java:
OUTPUT - http://prntscr.com/nx3zvj

CODE - http://prntscr.com/nx40sz
A do while loop? Haven't seen those in a while
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BiologyBoy2019
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Ye man I barely use them, so when I get an opportunity I chuck em in there
(Original post by whyamialive)
A do while loop? Haven't seen those in a while
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IWantDie
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I think question 1 was 4, 2, 2 marks. It's 8 in total.
For 1.1 you also track whether you made any changes every loop. If you don't make any changes then you can stop.

2 is 9 marks in total
2.2). What's the purpose of the turing machine? (1) I put something about it copying the first block of 1s it could find after a 0.
can't remember 2.4, it does exist though.

3 is 7 in total
3.2). what is representational abstraction
3.3). what is abstraction by generalisation (or maybe the other way round)
3.4). what other detail is missing? (1) I mentioned the fact that the puzzle is in a grid, dunno if that's right though
3.5). not sure
3.6). When would you use the bottom half of the graph? (1) If it was directional

I think 4 was 1,1,3. It's 5 marks in total

5). Code to check whether one word is a subset of another. 13 marks

6, 7, 8 are 2, 10, 6 marks. I can't remember the numbers, but a few questions I remember were
Name a user-defined function which uses error handling
Why did they choose to use a binary file

9.1). Create and explain the set which contains all useable items in the current game state. (useable Items in location) union (items in inventory intersection items with a use command). I think it's (E + B*D).
9.2). Explain why you can't create a set of all gettable items? Because if an item is in a container in the location it can be gotten
Rest of 9 was on the tip of my tongue, but can't remember now,
All parts of 9 are 1 mark.

10). Make the error message random (5)
11). Inventory size limit (8)
12). Drop Item (13)
13). Change the dice game to have a score (9)
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whyamialive
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(Original post by BiologyBoy2019)
Question 1.2: A statement “when sorting a large list it’s said to be intractable but when the list is smaller it’s said to be tractable”

My safari elephant question solution in java:
OUTPUT - http://prntscr.com/nx3zvj

CODE - http://prntscr.com/nx40sz
I should have done it your way but i did some dumb round about way because it just flew over my head:
https://prnt.sc/nxeh87
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whyamialive
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(Original post by IWantDie)
I think question 1 was 4, 2, 2 marks. It's 8 in total.
For 1.1 you also track whether you made any changes every loop. If you don't make any changes then you can stop.

2 is 9 marks in total
2.2). What's the purpose of the turing machine? (1) I put something about it copying the first block of 1s it could find after a 0.
can't remember 2.4, it does exist though.

3 is 7 in total
3.2). what is representational abstraction
3.3). what is abstraction by generalisation (or maybe the other way round)
3.4). what other detail is missing? (1) I mentioned the fact that the puzzle is in a grid, dunno if that's right though
3.5). not sure
3.6). When would you use the bottom half of the graph? (1) If it was directional

I think 4 was 1,1,3. It's 5 marks in total

5). Code to check whether one word is a subset of another. 13 marks

6, 7, 8 are 2, 10, 6 marks. I can't remember the numbers, but a few questions I remember were
Name a user-defined function which uses error handling
Why did they choose to use a binary file

9.1). Create and explain the set which contains all useable items in the current game state. (useable Items in location) union (items in inventory intersection items with a use command). I think it's (E + B*D).
9.2). Explain why you can't create a set of all gettable items? Because if an item is in a container in the location it can be gotten
Rest of 9 was on the tip of my tongue, but can't remember now,
All parts of 9 are 1 mark.

10). Make the error message random (5)
11). Inventory size limit (8)
12). Drop Item (13)
13). Change the dice game to have a score (9)
for 3.4 i wrote that they reduced the number of cells.
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BiologyBoy2019
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Also one of the questions asked the time complexity of a method in skeleton, it was n worst case
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whyamialive
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(Original post by BiologyBoy2019)
Also one of the questions asked the time complexity of a method in skeleton, it was n worst case
Yeah i put that. Wasn't it for the getIndexOfItem?
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BiologyBoy2019
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Ye man I think that was it 😀
(Original post by whyamialive)
Yeah i put that. Wasn't it for the getIndexOfItem?
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BiologyBoy2019
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Also one of the questions was what type of graph needs the all of the cells filled, I said a graph with weighted edges? Although I thought of bidirectional too?
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whyamialive
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(Original post by BiologyBoy2019)
Also one of the questions was what type of graph needs the all of the cells filled, I said a graph with weighted edges? Although I thought of bidirectional too?
I put down directional graph because the graph was technically weighted. It's just that it was weighted with only the number 1.
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BiologyBoy2019
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ye man i think the answer was unidirectional graph, damn
(Original post by whyamialive)
I put down directional graph because the graph was technically weighted. It's just that it was weighted with only the number 1.
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whyamialive
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(Original post by BiologyBoy2019)
ye man i think the answer was unidirectional graph, damn
How do you think the rest of your theory and programming went? The programming went A-OK for me but i BS'ed the theory so hard
Last edited by whyamialive; 3 months ago
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danwillm
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I think for 1.2 it was why doesn't a problem become intractable when it is given a larger input, not just a sorting algorithm
(Original post by RedEyeBen)
1.1) Improve the bubble sort (2marks) ; Avoid checking the last n-1 items on the nth pass through the algorithm as you know they will already be in order.
1.2)Why doesnt a sorting algorithm become intractable?; for an algorithm to be intractable it needs to have an exponential time complexity or greater. A bubble sort only has a time complexity of O(n^2) and a merge sort has O(nlogn).
1.3) how to solve an intractable problem?; use a heuristic approach, relying on your past experiences to give an estimate of a solution.
2.1) trace the turing machine; https://www.thestudentroom.co.uk/att...4&d=1559580948
2.2) ???
2.3) ???
2.4) ???
3.1) Soduku grid ; ???
3.2) ???
3.3) ??
3.4) ??
3.5) ??
3.6) ??
4.1) What does * mean ; Zero or more occurences of previous character
4.2) What does ? mean; Zero or one occurence of the previous character
4.3) Which strings are valid?; ???
Section B
5.1) ???
5.2) ???
Section C
6.0) ???
7.1) ???
7.2) ???
7.3) ???
7.4) ???
7.5) ???
7.6) ???
8.1) ???
8.2) ???
8.3) ???
8.4) ???
9.1) ???
9.2) ???
9.3) ???
9.4) ???
9.5) ???
Section D
10.1) ???
10.2) ???
11.1) ???
11.2) ???
12.1)???
12.2)??
13.1)???
13.2)???


comment any more questions/answers and ill add them to this post
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BiologyBoy2019
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Programming was awesome, thought every 1 was fine.

Did alright, confused about the sets since didnt revise much on that, bottled the graph question we just talked about and can't remember many other questions - liked the sudoku one tho as I do sudoku at home when I'm bored, although why they chose to use letters instead of numbers I do not know haha (a= 1, b=2, c=3, d=4, e=5, f=6, g=7, h=8, i=9)

What about u, did u forget anything when u were in there
(Original post by whyamialive)
How do you think the rest of your theory and programming went? The programming went A-OK for me but i BS'ed the theory so hard
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whyamialive
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(Original post by BiologyBoy2019)
Programming was awesome, thought every 1 was fine.

Did alright, confused about the sets since didnt revise much on that, bottled the graph question we just talked about and can't remember many other questions - liked the sudoku one tho as I do sudoku at home when I'm bored, although why they chose to use letters instead of numbers I do not know haha (a= 1, b=2, c=3, d=4, e=5, f=6, g=7, h=8, i=9)

What about u, did u forget anything when u were in there
I think i lost a few marks on the bubble sort question because i didn't talk about not comparing the values after n-1 passes. I also forgot about using a heuristic approach, when solving intractable problems, as i forgot to revise for it :rolleyes:. The soduku was surprisingly easy even if i've never done a sudoku puzzle before, although they did fill out nearly every single cell.

The set question left me slightly traumatised and alot of people got different answers for those.

Let's just hope P2 doesn't screw us over
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kiantigger
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Thought I'd update the mark scheme. Sorry if any of it's wrong!
1.1) Improve the bubble sort; (4 marks)
Avoid checking the last n-1 items on the nth pass through the algorithm as you know they will already be in order. Track whether changes have been made every loop: if you don’t make any you can stop.
1.2)Why doesn’t a sorting algorithm become intractable?; (2 marks)
for an algorithm to be intractable it needs to have an exponential time complexity or greater. A bubble sort only has a time complexity of O(n^2) and a merge sort has O(nlogn).
1.3) how to solve an intractable problem?; (2 marks)
use a heuristic approach, relying on your past experiences to give an estimate of a solution.
2.1) trace the turing machine; https://www.thestudentroom.co.uk/att...4&d=1559580948
2.2) What is the purpose of a turing machine? (1 mark)
Turning any binary number into a palindrome?
2.3) What does the term universal Turing machine mean;
2.4) ???
2 is 9 marks total
3.1) Soduku grid ; ???
3.2) What is procedural abstraction.
3.3) What is abstraction by generalisation.
3.4) What other detail is missing? (From the puzzle to the grid) (1 mark)
3.5) ??
3.6) When would you use the bottom half of the graph? (1 mark)
If the graph was directional.
4.1) What does * mean ; Zero or more occurences of previous character (1 mark)
4.2) What does ? mean; Zero or one occurence of the previous character (1 mark)
4.3) Which strings are valid?; (3 marks)
1|01* ( I think) Don’t remember rest of the strings sorry.
1 Y





Section B
5.1) Code to check if one word was a subset of another (E.G. eat and ate) (12 marks)
5.2) Screenprints of using NINE and ELEPHANTINE and NINE and ELEPHANT. (1 mark)
Section C
6.0) Why would you use a binary file. (2 marks)
7.1) ???
7.2) ???
7.3) ???
7.4) ???
7.5) ???
7.6) ???
8.1) ???
8.2) ???
8.3) ???
8.4) ???
9.1) Create and explain the set which contains all useable items in the current game state. (1 mark)
(useable items in location union items in inventory intersection items with a use command).
9.2) Explain why intersections of set A and F would not contain be the set that contains just the useable items in the current location? ( 1 mark)
9.3) ??? (1 mark)
9.4) ??? (1 mark)
9.5) ??? (1 mark)
Section D
10.1) Make the error message random (4)
10.2) Screen prints (1)
11.1) Inventory size limit (7)
11.2) Screen prints (1)
12.1)Drop item (12)
12.2)Screen prints(1)
13.1)Change dice game to be 100*largest + 10*middle + lowest for player and 100*last + 10*second + first for othercharacter. Display score and stuffs. (8)
13.2)Screen prints(1)
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