CDE

Task/Digital-root/Java/digital-root.java

@@ -0,0 +1,31 @@
+import java.math.BigInteger;
+
+class DigitalRoot
+{
+  public static int[] calcDigitalRoot(String number, int base)
+  {
+    BigInteger bi = new BigInteger(number, base);
+    int additivePersistence = 0;
+    if (bi.signum() < 0)
+      bi = bi.negate();
+    BigInteger biBase = BigInteger.valueOf(base);
+    while (bi.compareTo(biBase) >= 0)
+    {
+      number = bi.toString(base);
+      bi = BigInteger.ZERO;
+      for (int i = 0; i < number.length(); i++)
+        bi = bi.add(new BigInteger(number.substring(i, i + 1), base));
+      additivePersistence++;
+    }
+    return new int[] { additivePersistence, bi.intValue() };
+  }
+
+  public static void main(String[] args)
+  {
+    for (String arg : args)
+    {
+      int[] results = calcDigitalRoot(arg, 10);
+      System.out.println(arg + " has additive persistence " + results[0] + " and digital root of " + results[1]);
+    }
+  }
+}