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D1 (Decision 1) 17 May 2013 Official Thread Watch

1. (Original post by Flounder1)
You look at how much of a float it has and then just see in your mind (if without a Gantt chart) if the event can happen on each before or after day 20 without delaying the project
If it delays it then its a must?
If it doesn't then it's a may? I think I don't want to screw up your knowledge

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do you have more questions , please scan and I can see good revision

Define: tree
define:spanning tree
define: bipartite graph

total 6 marks ! ill mark it
3. (Original post by Westeros)
I'm kinda' with you on that, they're both right at the bottom, definitely! I just hate finding the optimal solution etc on Linear Programming! I really hope I get an A in this exam!

My Sun and Stars
yeah the optimals are a bit of a pain to do, especially when it's not an integer same, if anything I need to learn all the definitions but there are so many! Same, good luck!

Haha, it's ok, I'm a bit of a Game of Thrones fan too, Moon of My World
4. (Original post by otrivine)

Define: tree
define:spanning tree
define: bipartite graph

total 6 marks ! ill mark it
A tree is a connected graph with no cycles.
A spanning tree is a subgraph that contains all of the vertices of the graph and is also a tree.
A bipartite graph is a graph that has two sets of verticces in which arcs may only connect vertices in one set to vertices in the other set or vice versa.
5. (Original post by Epic Flawless)
A tree is a connected graph with no cycles.
A spanning tree is a subgraph that contains all of the vertices of the graph and is also a tree.
A bipartite graph is a graph that has two sets of verticces in which arcs may only connect vertices in one set to vertices in the other set or vice versa.
yes nicely said

my turn
6. (Original post by otrivine)

Define: tree
define:spanning tree
define: bipartite graph

total 6 marks ! ill mark it
A tree is a connected graph with no cycles

A spanning tree is a subgraph of say graph G, whose nodes and arcs all belong to G. It is also a tree.

A bipartite graph is a graph that consists of 2 sets of nodes, say sets A and B, where arcs connect nodes in different sets. E.g. an arc connects a node from set A to a node in set B. Nodes in the same set cannot be connected to each other.
7. (Original post by otrivine)
yes nicely said

my turn
Define:
Path
Alternating path
Matching

Btw, how long does it take for you to complete a paper?
8. (Original post by TanishaBellum)
A tree is a connected graph with no cycles

A spanning tree is a subgraph of say graph G, whose nodes and arcs all belong to G. It is also a tree.

A bipartite graph is a graph that consists of 2 sets of nodes, say sets A and B, where arcs connect nodes in different sets. E.g. an arc connects a node from set A to a node in set B. Nodes in the same set cannot be connected to each other.
Correct
9. A path is a finite sequence of arcs where the end vertex of an edge is the start vertex of the next edge. In a path no vertex can be visited more than once.

An alternating path is where you start from a node not in the initial matching then connect to a node in the matching and so on. So not in matching and in matching. Must start and end at nodes not in the initial matching. (poor explanation)

A matching is where some or all the nodes in set A are connected to nodes in set B.

Okay these were hard LOL sorry for butting in
10. (Original post by otrivine)
Correct
Btw does a spanning tree have to contain ALL the nodes from the tree?
11. (Original post by TanishaBellum)
A path is a finite sequence of arcs where the end vertex of an edge is the start vertex of the next edge. In a path no vertex can be visited more than once.

An alternating path is where you start from a node not in the initial matching then connect to a node in the matching and so on. So not in matching and in matching. Must start and end at nodes not in the initial matching. (poor explanation)

A matching is where some or all the nodes in set A are connected to nodes in set B.

Okay these were hard LOL sorry for butting in
The more succinct definition for an alternating path is:
An alternating path is a path from an unmatched vertex in one set to an unmatched vertex in the other set using arcs alternately not in/in the initial matching.

The definition for matching isn't quite right:
A matching is a one-to-one pairing between some of the vertices in one set to some of the vertices in the other set.
12. (Original post by Epic Flawless)
Define:
Path
Alternating path
Matching

Btw, how long does it take for you to complete a paper?
Path is a finite sequence of event such that the end vertex is the start vertex of the next but the vertex does not appear more than once.

Alternating path is a path in which the unmatched vertex of x matches to an unmatched vertex in Y that alternately uses arcs in/not in the matching.

mathcing is the 1-1 pairing of all or some of the elements of x to the elements in Y.

To be honest I finish exactly in 90minutes and u
13. (Original post by Epic Flawless)
Define:
Path
Alternating path
Matching

Btw, how long does it take for you to complete a paper?
I struggled with time A LOT but having done past papers i've become better at managing time. I usually have about 40-45 minutes for the last 2 questions and I spend around 30 minutes doing the first 3 questions which is long IMO. I want to speed up!

14. (Original post by TanishaBellum)
Btw does a spanning tree have to contain ALL the nodes from the tree?

yes so its all the nodes included
15. (Original post by TanishaBellum)
Btw does a spanning tree have to contain ALL the nodes from the tree?
It does indeed. You defined a subgraph, apart from the last bit about the tree?
16. (Original post by otrivine)
Path is a finite sequence of event such that the end vertex is the start vertex of the next but the vertex does not appear more than once.

Alternating path is a path in which the unmatched vertex of x matches to an unmatched vertex in Y that alternately uses arcs in/not in the matching.

mathcing is the 1-1 pairing of all or some of the elements of x to the elements in Y.

To be honest I finish exactly in 90minutes and u
I finish in about 50-55 mins before checking which makes me quite nervous because I normally finish in about 40-45 mins for non-Decision papers. :/
17. (Original post by Epic Flawless)
I finish in about 50-55 mins before checking which makes me quite nervous because I normally finish in about 40-45 mins for non-Decision papers. :/

I literally do a question and check it and then never come back to it so less time consuming.

are my defintions correct?
18. (Original post by Epic Flawless)
I finish in about 50-55 mins before checking which makes me quite nervous because I normally finish in about 40-45 mins for non-Decision papers. :/
Thats really quick! How do you finish the paper so quickly!?
19. (Original post by otrivine)
I literally do a question and check it and then never come back to it so less time consuming.

are my defintions correct?
Of course, they are!

I'm worried about making a mistake in the exam, because I know that would be deadly in decision since the following questions always stem from the first (e.g inspection, CPA, Dijkstra's). Especially because I was making silly mistakes in the mechanics exam, but fortunately, I had enough time to check, idenify and correct them.
20. (Original post by TanishaBellum)
Thats really quick! How do you finish the paper so quickly!?
I've just had a lot of practice since I do D2 as well. I can do the simple algorithms fairly quickly (e.g sorting/bin packing/ MST) and there are some tricks too to ensure that you don't make mistakes when you are applying the algorithms.

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