Removing duplicates/ignoring them from a 2 dimensional Array

Question

I have a bool[,] Array for keeping track of Nations that are either at war(true) or neutral(false).

The problem Im having is that when going over the matrix, to display al wars in UI elements, it will actually shwo duplicates of all wars, this is ofcourse obvious because: Nation 1 is at war with Nation 2. Nation 2 is at war with Nation 1. So it will ofcourse display both, but I just want one.

So how do I remove/ignore the duplicates?

Heres my code for generating the matrix:

It wont let me post images or code.

    public static void Init(Nation[] nationsArray)
    {
        nations = new List<Nation>(nationsArray);
        int numNations = nations.Count;

        enemyMatrix = new bool[numNations - 1, numNations - 1];

        for (int i = 0; i < numNations - 1; i++)
            nations[i].ID = i;
    }

    public static bool AreNationsEnemies(Nation nation1, Nation nation2)
    {
        return enemyMatrix[nation1.ID, nation2.ID];
    }

    public static void SetAsEnemies(Nation nation1, Nation nation2)
    {
        enemyMatrix[nation1.ID, nation2.ID] = true;
        enemyMatrix[nation2.ID, nation1.ID] = true;

        numberOfActiveWars++;
    }
    public static void SetAsNeutral(Nation nation1, Nation nation2)
    {
        enemyMatrix[nation1.ID, nation2.ID] = false;
        enemyMatrix[nation2.ID, nation1.ID] = false;

        numberOfActiveWars--;
    }
    }

So thats the problem, it displays the wars doubly so!

I appreciate any help, thanks in advance!

Answer 1

Consider only one half of the matrix. You can do it with

// Reading out the nations having war by eliminating the duplicates
for (int x = 0; x < numNations; x++) {
    for (int y = 0; y < x; y++) {
        // Here y is always < x, so we get e.g. x = 5, y = 3 but never x = 3, y = 5
        if (enemyMatrix[x, y]) {
             TODO: add nations nations[x], nations[y]
        }
    }
}

or, if you want y to be greater than x

   for (int y = x + 1; y < numNations; y++) {

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Btw. the declaration of the matrix should be

enemyMatrix = new bool[numNations, numNations]; // Without the -1

Because in C# you specify the size of the matrix dimensions and not the upper bounds as in VB.

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The matrix is automatically created with all the positions set to false. So, SetAsNeutral might not be necessary, unless you must change the values later.