A-M baby

Task/Modular-exponentiation/Ruby/modular-exponentiation-1.rb

@@ -0,0 +1,6 @@
+require 'openssl'
+
+a = 2988348162058574136915891421498819466320163312926952423791023078876139
+b = 2351399303373464486466122544523690094744975233415544072992656881240319
+m = 10 ** 40
+puts a.to_bn.mod_exp(b, m)

Task/Modular-exponentiation/Ruby/modular-exponentiation-2.rb

@@ -0,0 +1,18 @@
+class Integer
+  def rosetta_mod_exp(exp, mod)
+    exp < 0 and raise ArgumentError, "negative exponent"
+    prod = 1
+    base = self % mod
+    until exp.zero?
+      exp.odd? and prod = (prod * base) % mod
+      exp >>= 1
+      base = (base * base) % mod
+    end
+    prod
+  end
+end
+
+a = 2988348162058574136915891421498819466320163312926952423791023078876139
+b = 2351399303373464486466122544523690094744975233415544072992656881240319
+m = 10 ** 40
+puts a.rosetta_mod_exp(b, m)