A-M baby

Task/Modular-exponentiation/D/modular-exponentiation.d

@@ -0,0 +1,23 @@
+import std.stdio, std.bigint;
+
+BigInt powMod(BigInt base, BigInt exponent, BigInt modulus)
+in {
+   assert(exponent >= 0);
+} body {
+    BigInt result = 1;
+    while (exponent > 0) {
+        if (exponent % 2 == 1)
+            result = (result * base) % modulus;
+        exponent /= 2;
+        base = base ^^ 2 % modulus;
+    }
+    return result;
+}
+
+void main() {
+    powMod(BigInt("29883481620585741369158914214988194" ~
+                  "66320163312926952423791023078876139"),
+           BigInt("235139930337346448646612254452369009" ~
+                  "4744975233415544072992656881240319"),
+           BigInt(10) ^^ 40).writeln();
+}