Matrix element comparison

Question

I have some problems with comparison of matrix elements. Here is the code:

int coll = 0;
for (int i = 0; i < 9; i++)
{
    for (int j = 0; j < 9; j++)
    {
        int tmp = 0;
        for (int k = 0; k < 9; k++)
        {
            if (matrix[i, j] == matrix[i, k])
            {
                tmp++;
                Console.WriteLine("{0},{1} coll {2},{3}-al", i, j, i, k);
            }
            coll += tmp;
        }

    }
}

The code wants to compare the elements of an array called matrix. When 2 elements in a column are the same, I'll increase the tmp value. At the end coll will be increased by the number of the collisions of the actual element of the array. The problem is that the program will find only the collisions of the element with itself. For example, for a matrix like

the 0:0 position will collide only with itself and not with 1:0. Can anyone tell me why?

Whats the definition of matrix? The matrix is 9x9? Working on a sudoku solver? — Jeroen van Langen, Oct 02 '14 at 09:04
What is the type of `matrix`? Is it `int[,]` or `object[,]`? — Henrik, Oct 02 '14 at 09:04
I'm working on a sudoku solver but first I need to generate a table with the specific rules. The matrix is int[,]. I use integer lists to avoid the collisions int the rows and to make the generating a bit faster. But it's containing integer values as the matrix does. — Andras Csendes, Oct 03 '14 at 10:00

score 0 · Answer 1 · edited May 23 '17 at 12:21

Try this logic:

class Program
{
    static void Main(string[] args)
    {
        int[,] matrix=new int[,] {
            { 1, 2, 3, 4 },
            { 1, 3, 4, 2 },
            { 2, 3, 4, 1 },
            { 2, 4, 1, 3 } };

        // This returns the #of collisions in each column
        Debug.WriteLine(CheckColumn(matrix, 0));    // 2
        Debug.WriteLine(CheckColumn(matrix, 1));    // 1
        Debug.WriteLine(CheckColumn(matrix, 2));    // 1
        Debug.WriteLine(CheckColumn(matrix, 3));    // 0
    }

    static int CheckColumn(int[,] matrix, int column)
    {
        int[] data=new int[matrix.GetLength(0)];
        for(int i=0; i<data.Length; i++)
        {
            data[i]=matrix[i, column];
        }
        var hist=data.GroupBy(i => i)
            .OrderByDescending(g => g.Count())
            .Select(g => new { Num=g.Key, Dupes=g.Count()-1 })
            .Where(h=>h.Dupes>0);

        return hist.Count()>0?hist.Sum(h=>h.Dupes):0;
    }
}

I used code from https://stackoverflow.com/a/10335326/380384

Matrix element comparison

1 Answers1