2016 Update

Task/Aliquot-sequence-classifications/Java/aliquot-sequence-classifications.java

@@ -0,0 +1,62 @@
+import java.util.*;
+import java.util.stream.LongStream;
+import static java.util.stream.LongStream.rangeClosed;
+
+public class AliquotSequenceClassifications {
+
+    public static Long properDivsSum(long n) {
+        return rangeClosed(1, (n + 1) / 2).filter(i -> n % i == 0 && n != i).sum();
+    }
+
+    static boolean aliquot(long n, int maxLen, long maxTerm) {
+        List<Long> s = new ArrayList<>(maxLen);
+        s.add(n);
+        long newN = n;
+
+        while (s.size() <= maxLen && newN < maxTerm) {
+
+            newN = properDivsSum(s.get(s.size() - 1));
+
+            if (s.contains(newN)) {
+
+                if (s.get(0) == newN) {
+
+                    switch (s.size()) {
+                        case 1:
+                            return report("Perfect", s);
+                        case 2:
+                            return report("Amicable", s);
+                        default:
+                            return report("Sociable of length " + s.size(), s);
+                    }
+
+                } else if (s.get(s.size() - 1) == newN) {
+                    return report("Aspiring", s);
+
+                } else
+                    return report("Cyclic back to " + newN, s);
+
+            } else {
+                s.add(newN);
+                if (newN == 0)
+                    return report("Terminating", s);
+            }
+        }
+
+        return report("Non-terminating", s);
+    }
+
+    static boolean report(String msg, List<Long> result) {
+        System.out.println(msg + ": " + result);
+        return false;
+    }
+
+    public static void main(String[] args) {
+        long[] arr = {11L, 12, 28, 496, 220, 1184,  12496, 1264460,
+                           790, 909, 562, 1064, 1488};
+
+        LongStream.rangeClosed(1, 10).forEach(n -> aliquot(n, 16, 1L << 47));
+        System.out.println();
+        Arrays.stream(arr).forEach(n -> aliquot(n, 16, 1L << 47));
+    }
+}