Initial data commit

Task/Matrix-exponentiation-operator/C-sharp/matrix-exponentiation-operator.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using static System.Linq.Enumerable;
+
+public static class MatrixExponentation
+{
+    public static double[,] Identity(int size) {
+        double[,] matrix = new double[size, size];
+        for (int i = 0; i < size; i++) matrix[i, i] = 1;
+        return matrix;
+    }
+
+    public static double[,] Multiply(this double[,] left, double[,] right) {
+        if (left.ColumnCount() != right.RowCount()) throw new ArgumentException();
+        double[,] m = new double[left.RowCount(), right.ColumnCount()];
+        foreach (var (row, column) in from r in Range(0, m.RowCount()) from c in Range(0, m.ColumnCount()) select (r, c)) {
+            m[row, column] = Range(0, m.RowCount()).Sum(i => left[row, i] * right[i, column]);
+        }
+        return m;
+    }
+
+    public static double[,] Pow(this double[,] matrix, int exp) {
+        if (matrix.RowCount() != matrix.ColumnCount()) throw new ArgumentException("Matrix must be square.");
+        double[,] accumulator = Identity(matrix.RowCount());
+        for (int i = 0; i < exp; i++) {
+            accumulator = accumulator.Multiply(matrix);
+        }
+        return accumulator;
+    }
+
+    private static int RowCount(this double[,] matrix) => matrix.GetLength(0);
+    private static int ColumnCount(this double[,] matrix) => matrix.GetLength(1);
+
+    private static void Print(this double[,] m) {
+        foreach (var row in Rows()) {
+            Console.WriteLine("[ " + string.Join("   ", row) + " ]");
+        }
+        Console.WriteLine();
+
+        IEnumerable<IEnumerable<double>> Rows() =>
+            Range(0, m.RowCount()).Select(row => Range(0, m.ColumnCount()).Select(column => m[row, column]));
+    }
+
+    public static void Main() {
+        var matrix = new double[,] {
+            { 3, 2 },
+            { 2, 1 }
+        };
+
+        matrix.Pow(0).Print();
+        matrix.Pow(1).Print();
+        matrix.Pow(2).Print();
+        matrix.Pow(3).Print();
+        matrix.Pow(4).Print();
+        matrix.Pow(50).Print();
+    }
+
+}