Multidimensional Arrays?

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  1. #1
    Registered User CreatedByShadow's Avatar
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    Multidimensional Arrays?

    What are multidimensional arrays used for? Until recently, I haven't found much use for them until I read something about designing a grid and it says use a multidimensional array with the sizes of the grid to your liking (i.e. if you want the grid to be 20x40, than it'll look like this: int grid[20][40]).

    I dont really understand them and how to use them.

  2. #2
    and the hat of wrongness Salem's Avatar
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    Your screen is a 2D array of pixels / characters.
    A map for a game could be a 2D array.
    Matrices are often stored in a 2D array.

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    VA National Guard The Brain's Avatar
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    an array of an array of pointers is also another possible application.. like extracting data from a multiline edit box.. have the first dimension of the array stand for each line of text.. and have the second dimension stand for the line of text itself..

    Code:
    cout << text[2][0] ;       // would print out the second line of text...   until it reaches the '\0'  null terminator
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    Quote Originally Posted by Salem
    Your screen is a 2D array of pixels / characters.
    A map for a game could be a 2D array.
    Matrices are often stored in a 2D array.
    Unless you used specialised storage techniques, a matrix is usually a 2 (or more) dimensional array

    A map of the planets in a solar system would probably be three dimensional, as would a map of solar systems in a galaxy.

    If your program is to support display on multiple screens, it may use an array of screens. If each screen is a 2D array of pixels/characters than an array of screens could also be represented as a 3D array of pixels/characters.

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    Registered User CreatedByShadow's Avatar
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    Based on your replies, this is what I got.

    Multidimensional arrays can be used for text editing.
    Code:
    int text[4][20] = "16";
    Wouldnt that statment assign 16 to position 19 at line 4?

    And if I wanted to created a 2D map grid the size of 40x40, i would make it like below:
    Code:
    int map_grid[40][40];
    I think i grasp the basics of these. But isn't there a tutorial that explains these a bit more in-depth than the ones here?

  6. #6
    Just Lurking Dave_Sinkula's Avatar
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    Quote Originally Posted by CreatedByShadow
    Code:
    int text[4][20] = "16";
    Wouldnt that statment assign 16 to position 19 at line 4?
    No. That is a syntax error.

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    Registered User CreatedByShadow's Avatar
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    I want to know how to work with them. As of now, im completely lost at this...

  8. #8
    Just Lurking Dave_Sinkula's Avatar
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    Code:
    #include <iostream>
    #include <iomanip>
    
    int main()
    {
       int value[4][3] = { {1,2,3}, {4,5,6}, {7,8,9}, {10,11,12} };
       for ( int i = 0; i < 4; ++i )
       {
          for ( int j = 0; j < 3; ++j )
          {
             std::cout << std::setw(2) << value[i][j] << ' ';
          }
          std::cout << '\n';
       }
       return 0;
    } 
    
    /* my output
     1  2  3 
     4  5  6 
     7  8  9 
    10 11 12 
    */
    But it is always beneficial to have a problem to solve before you go looking for solutions.
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    40. There are two ways to write error-free programs; only the third one works.*

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