Task

Multiply two matrices together.

They can be of any dimensions, so long as the number of columns of the first matrix is equal to the number of rows of the second matrix.




public class Matrix
{
	int n;
	int m;
	double[,] a;
 
	public Matrix(int n, int m)
	{
		if (n <= 0 || m <= 0)
			throw new ArgumentException("Matrix dimensions must be positive");
		this.n = n;
		this.m = m;
		a = new double[n, m];
	}
 
	//indices start from one
	public double this[int i, int j]
	{
		get { return a[i - 1, j - 1]; }
		set { a[i - 1, j - 1] = value; }
	}
 
	public int N { get { return n; } }
	public int M { get { return m; } }
 
	public static Matrix operator*(Matrix _a, Matrix b)
	{
		int n = _a.N;
		int m = b.M;
		int l = _a.M;
		if (l != b.N)
			throw new ArgumentException("Illegal matrix dimensions for multiplication. _a.M must be equal b.N");
		Matrix result = new Matrix(_a.N, b.M);
		for(int i = 0; i < n; i++)
			for (int j = 0; j < m; j++)
			{
				double sum = 0.0;
				for (int k = 0; k < l; k++)
					sum += _a.a[i, k]*b.a[k, j];
				result.a[i, j] = sum;
			}
		return result;
	}
}