Multiply Matrices

This algorithm multiplies two given matrices

• C#
• VB.Net
• C
• C++
• PHP

									public struct Matrix
{
	public int[,] _Matrix;
	public int Rows;
	public int Columns;

	public Matrix(int[,] matrix, int rows, int columns)
	{
		this._Matrix = matrix;
		this.Rows = rows;
		this.Columns = columns;
	}
}

public static Matrix MultiplyMatrices(Matrix firstMatrix, Matrix secondMatrix)
{
	int[,] mult = new int[firstMatrix.Rows, secondMatrix.Columns];

	if (firstMatrix.Columns != secondMatrix.Rows)
		return default(Matrix);

	for (int i = 0; i < firstMatrix.Rows; ++i)
		for (int j = 0; j < secondMatrix.Columns; ++j)
		{
			mult[i, j] = 0;
		}

	for (int i = 0; i < firstMatrix.Rows; ++i)
		for (int j = 0; j < secondMatrix.Columns; ++j)
			for (int k = 0; k < firstMatrix.Columns; ++k)
			{
				mult[i, j] += firstMatrix._Matrix[i, k] * secondMatrix._Matrix[k, j];
			}

	return new Matrix(mult, firstMatrix.Rows, secondMatrix.Columns);
}
								

Example

									int[,] m1 = new int[2, 3];
m1[0, 0] = 3;
m1[0, 1] = -2;
m1[0, 2] = 5;
m1[1, 0] = 3;
m1[1, 1] = 0;
m1[1, 2] = 4;

int[,] m2 = new int[3, 2];
m2[0, 0] = 2;
m2[0, 1] = 3;
m2[1, 0] = -9;
m2[1, 1] = 0;
m2[2, 0] = 0;
m2[2, 1] = 4;

Matrix matrix1 = new Matrix(m1, 2, 3);
Matrix matrix2 = new Matrix(m2, 3, 2);
Matrix sumMatrix = MultiplyMatrices(matrix1, matrix2);
								

Output

									[0, 0] = 24
[0, 1] = 29
[1, 0] = 6
[1, 1] = 25