Express one dimension of 2d array as new array

Question

I have a 2d array a[3,3] . How can I express one dimension as a new array and pass it to some function?

int[,] a = new int[3,3];

a[0,0] = 1;

...

string b = concatenate(a[0]);     // where concatenate is a function
                                  // take a one dimension array as param

Also, can I create a 65000x65000 array with C#? I got some "out of memory" error.

Answer 1

The easiest way to handle this is to create a jagged array

int[][] i = new int[3][];

that way:

string b = concatenate(i[0]); will work.

To your second question you will run into issues with the LOH with objects approaching that size. This is probably not your problem though. I would look here as to a possible explanation as to why.

Answer 2

You will need to use jagged arrays .

int[][] a = new int[3][]
a[0] = new int[3];
a[1] = new int[3];
a[2] = new int[3];
a[0][0] = 1;
string b = concatentate(a[0]);

Also, creating a 65000x65000 array would result in 65000^2 = 4225000000 slots (or about 16GB or data) so it is no wonder that you are getting an OutOfMemoryException .

Answer 3

To answer your second question, a 65k x 65k two-dimensional array has more than 4 billion items; a 4-byte integer type would clock in at about 16GB in size. If you don't have enough memory on your box to initialize a 16GB block of memory, then, no, you cannot create a 65k x 65k array. And that's not even bothering with the addressing issues you'll run into trying to do a lookup on that array. Too big, man. Too big.

To answer your first question, a two-dimensional array is a unique construct that is incompatible with one-dimensional arrays. If you create a jagged array instead (which is an array of arrays), you'll be able to do what you want.

Answer 4

A 65000 by 65000 array of int s would take about 16 gigabytes of memory, so it's not surprising you got an out of memory error. I couldn't get a single .NET 3.5 application to allocate more than about 1.7GB of memory when I last tried, so no luck there.

As for passing one dimension to a function, it depends. You may be able to do what you want with a jagged array :

int[][] array = new int[3][];
for (int i = 0; i < array.Length; i++)
    array[i] = new int[3];

string b = concatenate(array[0]);

That way each position in the first dimension is its own array, which you can pass around (as in the last line). If you wanted to pass a row of items in the other 'direction', you'd have to copy items around first.

PS: You might want to look at String.Join and String.Concat for your concatenating needs. The second has a lot of overloads, but you probably need the first for displaying integers.