# Connection Array into an adjacency Matrix

Darren Jacobs

Greenhorn

Posts: 6

posted 10 years ago

Hi there,

I have a 2D array called conArray, which holds values that tell me which nodes are connected to which other nodes.

The format of the array is as follows:

0 1

0 A B

1 B C

2 D E

3 C E

With the numbers representing the location of the characters inside the array.

For example, the first line means that Node A is connected to Node B.

I have been trying to work out of a way of getting these values into an adjacency matrix so that the rows and columns of the matrix represent the characters, and a 1 or 0 is stored in the place when indexed by both of them.

For example, with the array above i would end up with a boolean adjacency matrix that looks like this:

0 1 2 3 4

0 F T F F F

1 T F T F F

2 F T F F T

3 F F F F T

4 F F T T F

where the numbers around the outside represent the characters..(e.g 0=A,1=B)

I can work out the conditional bit of asking whether they connect or not but I have no idea how to put the answer in the right place in the adjacency matrix, if you understand?

Sorry my explaining is a bit poor but many many thanks for any help.

I have a 2D array called conArray, which holds values that tell me which nodes are connected to which other nodes.

The format of the array is as follows:

0 1

0 A B

1 B C

2 D E

3 C E

With the numbers representing the location of the characters inside the array.

For example, the first line means that Node A is connected to Node B.

I have been trying to work out of a way of getting these values into an adjacency matrix so that the rows and columns of the matrix represent the characters, and a 1 or 0 is stored in the place when indexed by both of them.

For example, with the array above i would end up with a boolean adjacency matrix that looks like this:

0 1 2 3 4

0 F T F F F

1 T F T F F

2 F T F F T

3 F F F F T

4 F F T T F

where the numbers around the outside represent the characters..(e.g 0=A,1=B)

I can work out the conditional bit of asking whether they connect or not but I have no idea how to put the answer in the right place in the adjacency matrix, if you understand?

Sorry my explaining is a bit poor but many many thanks for any help.

Keith Lynn

Ranch Hand

Posts: 2409

posted 10 years ago

In Java, you can create arrays of arrays.

In your case, you could create an array of 5 elements and each element is an array of boolean.

You can use this like a 2-dimensional array, by filling in the first row and first column and then using loops to fill in the rest of the array.

If this isn't clear, let me know.

In your case, you could create an array of 5 elements and each element is an array of boolean.

You can use this like a 2-dimensional array, by filling in the first row and first column and then using loops to fill in the rest of the array.

If this isn't clear, let me know.

Yuriy Zilbergleyt

Ranch Hand

Posts: 429

posted 10 years ago

Well the matrix would just be an array of arrays, right? Then there are two simple ways of doing this:

1. Initialize the matrix to be all "F". Then go through every single connection and populate the correct places with "T".

2. The matrix starts empty. Have a nested for-loop go through every space in the matrix and check the connections array to see whether or not that spot should be populated, and put the correct value in the space.

Hope this helps,

Yuriy

1. Initialize the matrix to be all "F". Then go through every single connection and populate the correct places with "T".

2. The matrix starts empty. Have a nested for-loop go through every space in the matrix and check the connections array to see whether or not that spot should be populated, and put the correct value in the space.

Hope this helps,

Yuriy

Darren Jacobs

Greenhorn

Posts: 6

Yuriy Zilbergleyt

Ranch Hand

Posts: 429

posted 10 years ago

If you mean "which one to use" you have to decide that for yourself, just be consistent. Do you want [0][1] to represent "1 across, 0 down" or "0 down, 1 across"?

If you mean "what number represents B", just subtract the number 65 from the character 'B'. Make sure you use capital letters. I'd put the conversion code into a seperate method.

Yuriy

[ May 02, 2006: Message edited by: Yuriy Zilbergleyt ]

For example, if A is connected to B. I need to put a T in the adjacency matrix at [0][1] or [1][0]

If you mean "which one to use" you have to decide that for yourself, just be consistent. Do you want [0][1] to represent "1 across, 0 down" or "0 down, 1 across"?

If you mean "what number represents B", just subtract the number 65 from the character 'B'. Make sure you use capital letters. I'd put the conversion code into a seperate method.

Yuriy

[ May 02, 2006: Message edited by: Yuriy Zilbergleyt ]

Darren Jacobs

Greenhorn

Posts: 6

Yuriy Zilbergleyt

Ranch Hand

Posts: 429

Darren Jacobs

Greenhorn

Posts: 6

Keith Lynn

Ranch Hand

Posts: 2409

Darren Jacobs

Greenhorn

Posts: 6

posted 10 years ago

I've written that but it gives the error "operator cannot be applied to java.lang.String"

I'm guessing its not liking subtracting an integer from a string, how do i sort this?

I've written that but it gives the error "operator cannot be applied to java.lang.String"

I'm guessing its not liking subtracting an integer from a string, how do i sort this?