Data commit

Task/Rhonda-numbers/Java/rhonda-numbers.java

@@ -0,0 +1,62 @@
+public class RhondaNumbers {
+    public static void main(String[] args) {
+        final int limit = 15;
+        for (int base = 2; base <= 36; ++base) {
+            if (isPrime(base))
+                continue;
+            System.out.printf("First %d Rhonda numbers to base %d:\n", limit, base);
+            int numbers[] = new int[limit];
+            for (int n = 1, count = 0; count < limit; ++n) {
+                if (isRhonda(base, n))
+                    numbers[count++] = n;
+            }
+            System.out.printf("In base 10:");
+            for (int i = 0; i < limit; ++i)
+                System.out.printf(" %d", numbers[i]);
+            System.out.printf("\nIn base %d:", base);
+            for (int i = 0; i < limit; ++i)
+                System.out.printf(" %s", Integer.toString(numbers[i], base));
+            System.out.printf("\n\n");
+        }
+    }
+
+    private static int digitProduct(int base, int n) {
+        int product = 1;
+        for (; n != 0; n /= base)
+            product *= n % base;
+        return product;
+    }
+
+    private static int primeFactorSum(int n) {
+        int sum = 0;
+        for (; (n & 1) == 0; n >>= 1)
+            sum += 2;
+        for (int p = 3; p * p <= n; p += 2)
+            for (; n % p == 0; n /= p)
+                sum += p;
+        if (n > 1)
+            sum += n;
+        return sum;
+    }
+
+    private static boolean isPrime(int n) {
+        if (n < 2)
+            return false;
+        if (n % 2 == 0)
+            return n == 2;
+        if (n % 3 == 0)
+            return n == 3;
+        for (int p = 5; p * p <= n; p += 4) {
+            if (n % p == 0)
+                return false;
+            p += 2;
+            if (n % p == 0)
+                return false;
+        }
+        return true;
+    }
+
+    private static boolean isRhonda(int base, int n) {
+        return digitProduct(base, n) == base * primeFactorSum(n);
+    }
+}