dynamic multidimensional array 1

[Arainxius]

I need to read from the file and depending upon the three values I need a dynamic array that is something like

int array3D [frame][height][width]

I don't know the three parameters(frame, height, width) at compile time.


Then i want to read the datafile frame by frame
fread(df, sizeof(int), (height*width), fp)

and then assign it to
array3D[0][0][0] to array3D[0][height][width]

and then read second frame and assign to
array3D[1][0][0] to array3D[1][height][width]

and so on...

any help

thanks

 

[cpjust]

Use a vector:

typedef vector<int>           intVector_t;
typedef vector<intVector_t>   intVector2D_t;
typedef vector<intVector2D_t> intVector3D_t;

intVector3D_t array3D;

for ( int frame = 0; frame < maxFrames; ++frame )
{
   intVector2D_t array2D;

   for ( int height = 0; height < maxHeight; ++height )
   {
      intVector_t array;

      for ( int width = 0; width < maxWidth; ++width )
      {
         // Read num from your file...

         array.push_back( num );  // Add num to end of array.
      }

      array2D.push_back( array );  // Add array to end of 2D array.
   }

   array3D.push_back( array2D );  // Add 2D array to end of 3D array;
}

 

[Arainxius]

I just tried to compile the above code and it gives the following error

10 .typedef vector <int> intVector_t;
11. typedef vector<intVector_t> intVector2D_t;
12. typedef vector<intVector2D_t> intVector3D_t;

1>c:\temp\testarry\testarry\testarry.cpp(10) : error C2143: syntax error : missing ';' before '<'
1>c:\temp\testarry\testarry\testarry.cpp(10) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\temp\testarry\testarry\testarry.cpp(11) : warning C4091: 'typedef ' : ignored on left of 'int' when no variable is declared
1>c:\temp\testarry\testarry\testarry.cpp(11) : error C2143: syntax error : missing ';' before '<'
1>c:\temp\testarry\testarry\testarry.cpp(11) : error C2143: syntax error : missing ';' before '<'
1>c:\temp\testarry\testarry\testarry.cpp(12) : warning C4091: 'typedef ' : ignored on left of 'int' when no variable is declared
1>c:\temp\testarry\testarry\testarry.cpp(12) : error C2143: syntax error : missing ';' before '<'
1>c:\temp\testarry\testarry\testarry.cpp(12) : error C2143: syntax error : missing ';' before '<'

If it works then will i be able to access the individual data as array3D[j][k] ??

thanks

 

[cpjust]

Did you add these lines to your code:

#include <vector>
// your other #include lines...

using namespace std;
...

Yes, you can read the data like a normal array, but you must use the vector methods like push_back() to add data to it.

Here's the MSDN documentation for the STL vector class:

http://msdn2.microsoft.com/en-us/library/k449z507(VS.80).aspx

 

[Arainxius]

This is perfect. thanks.

However by using vectors the performance is very poor.
Code takes too much to execute.

 

[uolj]

However by using vectors the performance is very poor.

No. It is possible to use the vector in ways that lead to poor performance, but in general it will be roughly the same as a similar implementation with C style dynamic arrays. It does have the benefit of being safer and less bug prone, which is why you generally use vectors instead of dynamic arrays in C++.