Reverse a 3D array?

hugejeans

Hey all,

I've done the reverse a string before but does anyone have a suggestion for reversing this:

ushort[,,] TempArray = new ushort[700, 9, 2049];

for (j = 0; j < 1; j++) //lines
{
    for (i = 0; i < 9; i++)       //elements
    {
         for (k = 0; k < 2048; k++) //lines
         {
              TempArray[j, i, k] = CamData[bindex].Data[j, i, k];
         }
    }
}

(Camdata[].Data[] is already created and I am copying it into the TempArray[] to revese it)

Any idea's appriciated.

Giblet

You have the lengths of the arrays, and CamData is full i suppose?

Hint: 2048 - k.

hugejeans

Cheers Giblet,

Yes CamData is full, its filled from a seperate buffer, I tried this:

[code]
ushort[,,] TempArray = new ushort[700, 9, 2049];
x = 0;
y = 0;
z = 0;
for (j = 1; j > 0; j--) //lines
{
for (i = 9; i > 0; i--) //elements
{
for (k = 2048; k > 0; k--) //lines
{
TempArray[j, i, k] = CamData[bindex].Data[x, y, z];
z++;
}
y++;
}
x++
}
[\CODE]
But getting a System.IndexOutOfRangeException, although stepping through the code in debug the index into the arrays look fine.

Giblet

for (k = 0; k < 2048; k++) //lines
         {
              TempArray[j, i, k] = CamData[bindex].Data[1-j, 8-i, 2048 - k];
         }

That's the basic idea, but you have some other errors in there, but they're small index ones.

Could probably get the lengths of each dimension programmatically as well rather than hardcoding values. And remember ,Arrays are 0 based.
So an array with a size of 9, is referenced 0-8

hugejeans

Cheers Giblet,

I noticed the index problem scrolling through the the array values, silly mistake to make.

how would you suggest I get the lengths of each dimension programmatically, sizeof()?

Naikon

hugejeans wrote: »

Cheers Giblet,

I noticed the index problem scrolling through the the array values, silly mistake to make.

how would you suggest I get the lengths of each dimension programmatically, sizeof()?

I don't think sizeof() is applicable to Java. See, composite objects in Java are not aligned in memory as simply as say a load of structs ala C. I think the handiest way is to just use recursion. You could adapt something like the code below. Please note, I did not consider error checking below. Purely for illustration imo. Use at your own risk. I don't know off the top of my head how to do this in Java, but I reckon it should be somewhat similar. Maybe check out the Java/Oracle docs might have the answer?

#include <stdio.h>
#define LENGTH 6
int reverse(int *ptr, int length);

int main(int argc, char **argv) {
        int array[LENGTH] = { 5,4,3,2,1,0 };
        reverse(array, LENGTH-1);
        return 0; /*OS expects 0 as a sucess exit code. At least for Win/Unix*/
}

int reverse(int *ptr, int length) {
        if (length == 0) { /*Last int to print. Print it, then exit this func*/
                printf("%d\n", ptr[length]);
                return 0; /*Return 0 to indicate success*/
        }
        printf("%d\n", ptr[length]);
        reverse(ptr, length-1); /*Call the function again with a smaller problem set*/
        return 1; /*Assume 1 for non exit value of this function*/
}

hugejeans

Thanks Naikon,

Not Java, C#, I spose I should have mentioned that. I'm more of a C programmer so not really up to speed on the functions available in C#.

Nice example on using recursion to reverse an array, perfect for an interview

I'm trying to modify someelses code, very poorly designed code (15 thousand lines of code in one file).

Now that I have the 3D array reversing its not exactly what I need to do, I think I only need to reverse one of the dimensions. Will have to play arround with it a bit more.

Cheers lads.

Naikon

hugejeans wrote: »

Thanks Naikon,

Not Java, C#, I spose I should have mentioned that. I'm more of a C programmer so not really up to speed on the functions available in C#.

Nice example on using recursion to reverse an array, perfect for an interview

I'm trying to modify someelses code, very poorly designed code (15 thousand lines of code in one file).

Now that I have the 3D array reversing its not exactly what I need to do, I think I only need to reverse one of the dimensions. Will have to play arround with it a bit more.

Cheers lads.

No problem. Do as you wish with it, it's not there is anything copyrightable in it:pac: I don't know much about C# I admit, but it's a cousin of C, so there you go. 15K lines? Sorry to hear of your troubles:( Good luck.

tehjimmeh

hugejeans wrote: »

Cheers Giblet,

I noticed the index problem scrolling through the the array values, silly mistake to make.

how would you suggest I get the lengths of each dimension programmatically, sizeof()?

What you want is GetLength(), which returns the length of the dimension passed to it. i.e. GetLength(0) returns the length of the first dimension, GetLength(1) returns the length of the second dimension etc.

So to loop through a 3d array called 'arr' (where you want more control over the elements than a simple foreach), you would do:

 for(int i=0; i < arr.GetLength(0); i++)
     for(int j=0; j < arr.GetLength(1); j++)
         for(int k=0; k < arr.GetLength(2); k++)
             .........

Naikon: there is sizeof in C# (http://msdn.microsoft.com/en-us/library/eahchzkf(v=vs.71).aspx), but it can only be used in an unsafe context. The unsafe keyword in C# allows you to use pointers, like in C (http://msdn.microsoft.com/en-us/library/chfa2zb8(v=vs.71).aspx).

But obviously, it's not something you'd be using routinely for just finding out the length of an array.

Naikon

tehjimmeh wrote: »

What you want is GetLength(), which returns the length of the dimension passed to it. i.e. GetLength(0) returns the length of the first dimension, GetLength(1) returns the length of the second dimension etc.

So to loop through a 3d array called 'arr' (where you want more control over the elements than a simple foreach), you would do:

 for(int i=0; i < arr.GetLength(0); i++)
     for(int j=0; j < arr.GetLength(1); j++)
         for(int k=0; k < arr.GetLength(2); k++)
             .........

Naikon: there is sizeof in C# (http://msdn.microsoft.com/en-us/library/eahchzkf(v=vs.71).aspx), but it can only be used in an unsafe context. The unsafe
keyword in C# allows you to use pointers, like in C (http://msdn.microsoft.com/en-us/library/chfa2zb8(v=vs.71).aspx).

But obviously, it's not something you'd be using routinely for just finding out the length of an array.

Cool, I didn't know C# allows pointers to be used in such a direct manner. I was under the impression that managed langs like C#/Java just outright don't allow it.