June 2018 Update

Task/Modular-inverse/C-sharp/modular-inverse.cs

@@ -0,0 +1,24 @@
+public class Program
+{
+    static void Main()
+    {
+        System.Console.WriteLine(42.ModInverse(2017));
+    }
+}
+
+public static class IntExtensions
+{
+    public static int ModInverse(this int a, int m)
+    {
+        if (m == 1) return 0;
+        int m0 = m;
+        (int x, int y) = (1, 0);
+
+        while (a > 1) {
+            int q = a / m;
+            (a, m) = (m, a % m);
+            (x, y) = (y, x - q * y);
+        }
+        return x < 0 ? x + m0 : x;
+    }
+}