N dimensional array index

[ichihgo]

How can I know the index of N dimensional array  ?? 

 

Ex.

3d Array

 

 

6 7 8

4 6 3

 

index 

 

275

 

 

C++

[Judahnator]

What language are you writing this in?

[ichihgo]

What language are you writing this in?

C++

[PlutoNZL]

What is the index of an array? How is the index of that array 275?

[Judahnator]

I dont know how to do it in C++

 

In php, if it helps at all, i would write it like so:

$example = array(     array (          1, 2, 3,     ),     array(          4, 5, 6,     ));

[Guest]

Do you mean cardinality? I don't understand the question.

[ichihgo]

Do you mean cardinality? I don't understand the question.

To store a 2D array in a 1D array, simply make a 1D array with size rows × columns, and take each row starting with the first and insert it into the 1D array. Now if you want to access array2D[i][j], convert the index of this cell to the corresponding index in the 1D array.

If you want to do this with a 3D array, you can visualize it as several layers each layer contains a single 2D array. Start with the first layer, do the previous steps, then the second layer, and so on.

Given the size of a N-Dimensional array and an index, you are asked to convert this index to the corresponding index in a 1D array.

[ichihgo]

 

To store a 2D array in a 1D array, simply make a 1D array with size rows × columns, and take each row starting with the first and insert it into the 1D array. Now if you want to access array2D[i][j], convert the index of this cell to the corresponding index in the 1D array.

If you want to do this with a 3D array, you can visualize it as several layers each layer contains a single 2D array. Start with the first layer, do the previous steps, then the second layer, and so on.

Given the size of a N-Dimensional array and an index, you are asked to convert this index to the corresponding index in a 1D array.

 

The first line of the input will be a single integer T, the number of test cases (1 ≤ T ≤ 50). Followed by the test cases, each test case starts with an integer N the number of dimensions of the array (1 ≤ N ≤ 15). Followed by two lines, each contains N numbers. The first line represents the sizes of the dimensions (1 ≤ size[i] ≤ 15). The second line represents the index that you are asked to convert (0 ≤ index[i]  <  size[i]).

[ichihgo]

There's some kind of equation But I kept searching and can't find it

[PlutoNZL]

edit: nevermind.

[fizzlesticks]

2d: index = (y * width) + x

3d: index = (((z * height) + y) * width) + x

 

edit:

3d can also be written as

(z * height * width) + (y * width) + x

so for higher order N you just keep adding another dimension at the front making 4th dimension

(w * 3rdDim * 2ndDim * 1stDim) + (z * 2ndDim * 1stDim) + (y * 1stDim) + x

[ichihgo]

2d: index = (y * width) + x

3d: index = (((z * height) + y) * width) + x

I did found the pattern but I'm can't get  the index to work 

[ichihgo]

2d: index = (y * width) + x

3d: index = (((z * height) + y) * width) + x

 

edit:

3d can also be written as

(z * height * width) + (y * width) + x

so for higher order N you just keep adding another dimension at the front making 4th dimension

(w * 3rdDim * 2ndDim * 1stDim) + (z * 2ndDim * 1stDim) + (y * 1stDim) + x

Can you explain it with numbers please ?