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

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Avatar for boyyo
boyyo
6
Original post by Midgeymoo17
If you ensure its dark/ you press reasonably (not like sketching in art) it should be alright- just the more sensitive scan will definitely not be used so do make sure it is dark.


ahh ok thanks
Original post by Midgeymoo17
Yeah thats nasty. Hoever is he sitting C4 or M2 that clashes?


He's sitting D1 and M2
Reply 402
Avatar for boyyo
boyyo
6
Does anyone know if there will be model answers posted for this??
Original post by target21859
What does named correctly mean? Do you have define each letter you pick? Also when doing a quick sort can you do it like this? Sorry for the bad paint use haha


Could someone confirm that this is a valid method for quick sort (full marks)? Because the way I've been taught is completely different to the markscheme.
Original post by NotNotBatman
No, actually it's because you couldn't show K depends on H because the node halfway through G wouldn't be there.


I'm talking about the diagram I drew
Original post by thelegend99
I saw something where you had to prove the no of valencies that are odd occur in pairs or something?


Key Question that comes up:colone:xplain why there must always be an even [or zero] number of vertices with oddvalency in every graph.Answer:

•

-Each edge contributes two to the sum of the degree hence the sum must be even. Therefore vertices with odd number of valencies must exist in pairs. Hence there is always an even number of odd valencies.

Hardest D1 paper anyone's ever done??
D1 Definitions by Arsey
Definitions for the D1 Exam (and what they really mean!)

Graphs
A graph G consists of points (vertices or nodes) which are connected by lines (edges or arcs). A graph is just some points joined together with lines.

A subgraph of G is a graph, each of whose vertices belongs to G and each of whose edges belongs to G. A subgraph is just part of a bigger graph.

If a graph has a number associated with each edge (usually called its weight) then the graph is called a weighted graph or network. A weighted graph is one with values, eg distance, assigned to the edges.

The degree or valency of a vertex is the number of edges incident to it. A vertex is odd (even) if it has odd (even) degree. The degree of a vertex is how many edges go into it.

A path is a finite sequence of edges, such that the end vertex of one edge in the sequence is the start vertex of the next, and in which no vertex appears more than once. A path describes a ‘journey’ around a graph, where no vertex is visited more than once.

A walk is a path where you may visit vertices more than once.

A cycle (circuit) is a closed path, i.e. the end vertex of the last edge is the start vertex of the first edge.

Two vertices are connected if there is a path between them. A graph is connected if all its vertices are connected. Two vertices are connected if you can walk along edges from one to the othe, in a connected graph all vertices are connected.

If the edges of a graph have a direction associated with them they are known as directed edges and the graph is known as a digraph. A digraph will have arrows on the edges.

A tree is a connected graph with no cycles.

A spanning tree of a graph G is a subgraph which includes all the vertices of G and is also a tree.

A minimum spanning tree (MST) is a spanning tree such that the total length of its arcs is as small as possible. (MST is sometimes called a minimum connector.)

A graph in which each of the n vertices is connected to every other vertex is called a complete graph. In a complete graph every vertex is directly connected to every other edge.

Matchings

A bipartite graph consists of two sets of vertices X and Y. The edges only join vertices in X to vertices in Y, not vertices within a set. (If there are r vertices in X and s vertices in Y then this graph is Kr,s.) A bipartite graph has two sets of nodes. Nodes of one set can only be matched to nodes of the other set.

A matching is the pairing of some or all of the elements of one set, X, with elements of a second set, Y. If every member of X is paired with a member of Y the matching is said to be a complete matching. In a matching some of one set are joined to the other. In a complete matching they’re all joined.

An Alternating Path starts at an unconnected vertex in one set and ends at an unconnected vertex in the other set. Edges alternate between those ‘not in’ and ‘in’ the initial matching.

http://www.thestudentroom.co.uk/showthread.php?t=2693603
Original post by Midgeymoo17
Graphs in pencil. Ensure pencil line is dark i.e. do not press lightly. A more sensitive scan is performed go graphs an diagrams so we can use pencil. All other writing back pen.


Does that includes drawing networks too? Cheers for the help.
Original post by Midgeymoo17
Me but I really not need to do D1 as my six other units: Fp1,FP2,D2,S2,S1 and S3 will be better.


D1 is a lot easier than majority of those modules, dont you think?
Reply 410
Avatar for FugFig
FugFig
5
Hi! Can anyone please tell me what definitions/theory we need to know apart from Chapter 2? Thank you!
Do you have to draw the objective line as a dotted line?

Also, can you leave dijkstra/network/Krusal/Prim/ etc in pencil or do you have to do them in pen?
(edited 7 years ago)
Original post by Unknow_n123


there was a past paper that had "float" too. It was so specific! I'm so tempted to not even bother with the definitions
Original post by Nikhilm
Do you have to draw the objective line as a dotted line?


no you dont. just label it objective line
Original post by Footyrulez
Hardest D1 paper anyone's ever done??


check grade boundaries. grade boundaries go as high as 67
Original post by CutieTootsie
no you dont. just label it objective line


Cool thanks, do you mind quickly asking my other question too?
Original post by CutieTootsie
there was a past paper that had "float" too. It was so specific! I'm so tempted to not even bother with the definitions


The float is just the amount of time an activity can be delayed without affecting the project duration. I'd say learn the key definitions e.g. float, the even number of vertices with odd valency, Spanning tree, MST etc.
Definitions could add up to 3-4 marks so its sort of useful to know them...
Original post by FugFig
Hi! Can anyone please tell me what definitions/theory we need to know apart from Chapter 2? Thank you!


Check my reply on post 408
image.jpg
Attachment not found
I'm confused with drawing the scheduling diagram for this, why would D come before E?
image.jpg273.3KB
Original post by Nikhilm
Do you have to draw the objective line as a dotted line?

Also, can you leave dijkstra/network/Krusal/Prim/ etc in pencil or do you have to do them in pen?


Pencil is fine as long as its HB (basically dark).

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