Painting lines

[jacek]

ru talking about an array or an array of structs of some sort? i was thinking about using linked lists but im not very sure about using them in qt...

There are many options. You can keep a list of nodes and each node can contain a list of edges. You can also keep a list of nodes and a list of edges.

First think what data you need to store and how would you like to access it, then choose a data structure that fits the best.

[therealjag]

how do i construct a list og edges then..i looked at the linked list library but then i got confused with qvector aswell..which one do i use?

[jacek]

how do i construct a list og edges then..i looked at the linked list library but then i got confused with qvector aswell..which one do i use?

It depends. You can add items to the list faster, but accessing elements randomly is much slower than in vector. If you plan to add a lot of items and you will only read the whole list at once, you should use linked list. If you will access single items, you should use a vector. There is also a QList which is something between linked list and a vector.

[therealjag]

hey again i was thinking of using an array of structs where my struct would be:

struct Link{

int n1;
int n2;
int capacity
}

how would i create an array of this??

[jacek]

QVector<Link> links;

QVector<Link> links;

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[ePharaoh]

no offense, but you really ought to learn some basics of data structures. there's no point in learning qt data-structures without knowing basic DS theory.

it is a bit like learning to use the harpoon, without knowing what a whale is

grab a text book on data-structures; trust me, it will go a long way to ease programming.

[therealjag]

no offense, but you really ought to learn some basics of data structures. there's no point in learning qt data-structures without knowing basic DS theory.

it is a bit like learning to use the harpoon, without knowing what a whale is

yeah you're probably right but its a project im doing and i dont have much time to do it which is why i havent gone about it the proper way. i guess in the summer i could read to my hearts content and not bother you guys all the time

[therealjag]

hey there i tried using the QVector to make my struct into an array but the program crashes when i try to run it. it compiles ok but there seems to be a problem with the way i am referencing the QVector...heres my code below:

links[0].n2 = QInputDialog::getInteger(this, tr("QInputDialog::getInteger()"),
            													tr("enter second node to link:"), 25, 0, 100, 1, &ok);
 
				if(ok)
				integerLabel->setText(tr("%1").arg(links[0].n2));

links[0].n2 = QInputDialog::getInteger(this, tr("QInputDialog::getInteger()"),
            													tr("enter second node to link:"), 25, 0, 100, 1, &ok);
													            
				if(ok)
				integerLabel->setText(tr("%1").arg(links[0].n2));

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any help would be much appreciated again

[jpn]

void QVector::append ( const T & value )
Inserts value at the end of the vector.

[therealjag]

hey there i tried .append() but it still didnt work. i get an error saying:

"not enough contextual info to determine type"

i tried it with the following piece of code:

links.capacity.append(topology[n1][n2]);

links.capacity.append(topology[n1][n2]);

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what am i doing wrong?

[jacek]

links.capacity.append(topology[n1][n2]);

What types do the links and links.capacity have?

[therealjag]

links is just my struct Link and it contains the integer which is called capacity..
my struct is shown below:

struct Link{
 
int n1;
int n2;
int capacity;
}

struct Link{

int n1;
int n2;
int capacity;
}

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the 2-d array is just an integer as well

[jacek]

int doesn't have an append() method. You probably wanted to invoke that method on some other object.