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D1 (Decision 1) 17 May 2013 Official Thread

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Original post by Dilzo999
I got 2.6989898 something not 2.01. THIS IS CONFUSING XD.


No I mean in general , if you had 2.01 would you round to 3 or 2
Original post by otrivine
No I mean in general , if you had 2.01 would you round to 3 or 2


It's always rounding up in D1 :smile:
Original post by Fortitude
It's always rounding up in D1 :smile:


thanks, so you round up in everything! right


Define: Digraph

then ask me :smile:
Original post by otrivine
thanks, so you round up in everything! right


Define: Digraph

then ask me :smile:


Ok :biggrin: digraph = graph in which its edges have a direction associated with them (directed edges)

For you, starting off nice ...Degree/Valency = ...:smile:
Original post by Fortitude
Ok :biggrin: digraph = graph in which its edges have a direction associated with them (directed edges)

For you, starting off nice ...Degree/Valency = ...:smile:




yes exactly right


degree/valency of a vertex is the number of arcs(edges)incident to it.
Original post by otrivine
yes exactly right


degree/valency of a vertex is the number of arcs(edges)incident to it.


That is correct :biggrin::biggrin:
Original post by Fortitude
That is correct :biggrin::biggrin:


:smile:


Define:loop
Original post by otrivine
:smile:


Define:loop


We need to know that?! :confused:
Original post by Fortitude
We need to know that?! :confused:



Well I guess, cause it was in the definition?


Loop is an edge where it starts and finishes at the same vertex/
Original post by otrivine
Well I guess, cause it was in the definition?


Loop is an edge where it starts and finishes at the same vertex/


So that was in the textbook? I just learnt the ones which were given in the spec :tongue:
Original post by Fortitude
So that was in the textbook? I just learnt the ones which were given in the spec :tongue:


OMG, you are right, I spent so much time as well learning these definitions not in our spec:colondollar:

ok ill give you a different one.


Define:tree
Original post by otrivine
OMG, you are right, I spent so much time as well learning these definitions not in our spec:colondollar:

ok ill give you a different one.


Define:tree


Tree = connected graph with no cycles

Define Matching :smile:
Original post by Fortitude
Tree = connected graph with no cycles

Define Matching :smile:


Perfect!


Matching is the 1-1 pairing of some or all of the vertices such that the elements of X joins to the elements of Y.
Original post by otrivine
Perfect!


Matching is the 1-1 pairing of some or all of the vertices such that the elements of X joins to the elements of Y.


Correct :smile:
Original post by Fortitude
Correct :smile:


Define:Minimum spanning tree


Give 3 differences between Kruskals and prims alogrithm
Original post by Fortitude
So that was in the textbook? I just learnt the ones which were given in the spec :tongue:


Your right ! What on earth am I doing :redface:
Original post by posthumus
Your right ! What on earth am I doing :redface:


Good Morning :smile:
Original post by otrivine
Define:Minimum spanning tree


Give 3 differences between Kruskals and prims alogrithm


MST = is a subgraph which includes all vertices & is also a tree in which the total length of all its edges is as small as possible.


•

Kruskal's starts from the smallest edge while in Prim's the starting vertex is given.

•

The spanning tree in Prim's 'grows' while in Kruskals it chaotic (there's probably a much better way of explaining this)

•

Can apply prim's from a matrix, you can't with kruskals



And while we're on this topic, how do you answer questions which ask that: a route has to be included in the MST which algorithm would you use & how would you adapt it ??:confused:
Original post by posthumus
Your right ! What on earth am I doing :redface:


I'm sure they will only ask the definitions that they've mentioned in the spec :smile:
Original post by Fortitude
MST = is a subgraph which includes all vertices & is also a tree in which the total length of all its edges is as small as possible.


•

Kruskal's starts from the smallest edge while in Prim's the starting vertex is given.

•

The spanning tree in Prim's 'grows' while in Kruskals it chaotic (there's probably a much better way of explaining this)

•

Can apply prim's from a matrix, you can't with kruskals



And while we're on this topic, how do you answer questions which ask that: a route has to be included in the MST which algorithm would you use & how would you adapt it ??:confused:



all correct :smile:


The answer is always Krusckals and you say you start with AB and DE (example). This is because with Krusckals alogrithm can be built with non connected sub trees while prims only the tree grows and has to be connected all the time

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