Efficient way to allow for an n-dimensional coordinate?

Question

I am currently building a program that will calculate a self-avoiding walk in n-dimensions. The program has to have a list of coordinates that it has previously visited. For a known maximum number of dimensions, I would simply make a vector of a position struct as such:

struct Position
{
    long int x;
    long int y;
    long int z;
    long int w;
    etc...
}

std::vector<Position> history;
Position currentSite;

But when programming for an n-dimensional position, I am not sure how to do that without making an array of n*walk_length in size.

Is there a more "correct" way to do it?

Note: I'm programming in C++.

A vector of `n` values, where each entry represents e.g. `x`, `y` etc. respectively? — Some programmer dude, Nov 13 '13 at 14:37
To the first comment: It is limited to the maximum number of dimensions I include in the struct. @JoachimPileborg, then how do I track a history of positions? A vector of a vector? — NictraSavios, Nov 13 '13 at 17:14

score 3 · Answer 1 · answered Nov 13 '13 at 14:37

3

If n is known at compile time, you could use std::array<long,n> to represent a position.

If n is not known until runtime, std::vector<long> would be a good choice.

answered Nov 13 '13 at 14:37

NPE

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n-dimensions, not n-variables. It would be n^walk_length variables. – NictraSavios Nov 13 '13 at 15:44
@NictraSavios: What I described would be used to represent one position. To represent a sequence of positions you'd use a vector of those just as you're doing already. – NPE Nov 13 '13 at 15:56

score 2 · Accepted Answer · answered Nov 13 '13 at 14:39

2

I'd use vector for coordinates, and set for positions:

typedef std:vector<long> Position;
typedef std::set<Position> VisitedPositions;

Then you'll be able to choose n dynamically and search for positions more quickly.

answered Nov 13 '13 at 14:39

HEKTO

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How would I be able to choose n dynamically if I don't have variables in my struct for it? I would need a struct that creates new objects. – NictraSavios Nov 13 '13 at 15:43
@NictraSavios - as far as I understood you needed a program which works with any n without changes, right? In this case it can request the n value from you interactively and keep all the coordinates in the vector. This case I call "dynamic". If you know the n in advance and it's not too big you can hardcode the structure with all the coordinates - it will be "static" case. – HEKTO Nov 13 '13 at 15:51
Yes, I'd like a dynamic case, so how could I create a dynamically dimensional vector? Would it be something like vector Which would produce a "table" of axis by value, step and value, like 3,3,-10 , which would mean w-axis (4d), 3rd step in the walk and at w=-10. – NictraSavios Nov 13 '13 at 17:13
@NictraSavios - no, I meant you save all your coordinates into the vector one by one using the _push_back_ function. So, the pos[0] will contain x-coordinate, pos[1] - y-coordinate and so on. The length of the vector will be equal to your dimensionality n. It's the same approach the NPE was talking about. – HEKTO Nov 13 '13 at 21:06

Efficient way to allow for an n-dimensional coordinate?

2 Answers2