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Thread: Multidimensional SortedList (C#)

  1. #1
    Senior Member
    Join Date
    Jan 2004

    Multidimensional SortedList (C#)

    I am trying to create a 2-Dimensional SortedList in C#. I need to be able to look up a value using two keys, much like x,y coordinates.

    See the table below. I need to be able to input two keys (A,C) and have the value '3' returned. The keys are an enumeration I have and the values will be integers. The standard C# SortedList only supports one key to one value. How can I best do this in C#?

    Using this:
    public enum letters
      A B C
    A 1 2 3
    B 2 3 1
    C 3 1 2
    Last edited by AxessTerminated; November 4th, 2007 at 09:53 PM.
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  2. #2
    Senior Member
    Join Date
    Jul 2001

    coming from a c world I would think a two dimensional array like int array [][]; You can use this directly array[A][C] bur I am not sure if that works for c#.

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  3. #3
    Senior Member
    Join Date
    Mar 2004

    If you want to go with the typesafe generics, you may think about
    an invertible mapping from your 2-d parameter space to a 1-d parameter
    space. Usually, there are two approaches for this:

    1. (A,B) -> "A_B"

    The function maps the two letters (A,B) to a string "A_B".
    Your SortedList thus is of type SortedList(of string,integer).

    2. (A,B) -> 5

    The function maps the two corresponding numbers to an integer
    using the function x*3+y:

    (A,A) = 4
    (A,B) = 5
    (A,C) = 6
    (B,A) = 7

    Your SortedList thus is of type SortedList(of integer,integer).

    If performance is an issue go with the latter (which does in principle
    the same as a 2-d array).

    If performance really is an issue you may think about using a
    SortedList/SortedDictionary versus an unsorted Dictionary: if you
    read more often than write, a SortedList/SortedDictionary is a good
    choice, otherwise use the Dictionary.

    ...Alternatively, you certainly could work with multidimensional arrays as
    proposed by dspeidel.

    I forgot: What you could do if performance is not an issue but
    nice design: create a class MyKey implementing IComparable
    on your custom class (storing the two keys (A,B)) such that you could use
    a SortedList/SortedDictionary(Of MyKey, Integer)

    Last edited by sec_ware; November 5th, 2007 at 09:54 AM.
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  4. #4
    Junior Member
    Join Date
    Nov 2007
    In Java it's just as follows. I don't know if there is a .length method/function in C# though!

    int[][] arrayName = new int[2][2];
    Then you could just tranverse the array with a nested loop to either look up a value or fill the array.

    (for int i=0; i < arrayName.length; i++)
      for(int j = 0; j < arrayName[i].length; j++)
         //do whatever
       // do whatever

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