Initial data commit

Task/Lychrel-numbers/Java/lychrel-numbers.java

@@ -0,0 +1,82 @@
+import java.math.BigInteger;
+import java.util.*;
+
+public class Lychrel {
+
+    static Map<BigInteger, Tuple> cache = new HashMap<>();
+
+    static class Tuple {
+        final Boolean flag;
+        final BigInteger bi;
+
+        Tuple(boolean f, BigInteger b) {
+            flag = f;
+            bi = b;
+        }
+    }
+
+    static BigInteger rev(BigInteger bi) {
+        String s = new StringBuilder(bi.toString()).reverse().toString();
+        return new BigInteger(s);
+    }
+
+    static Tuple lychrel(BigInteger n) {
+        Tuple res;
+        if ((res = cache.get(n)) != null)
+            return res;
+
+        BigInteger r = rev(n);
+        res = new Tuple(true, n);
+        List<BigInteger> seen = new ArrayList<>();
+
+        for (int i = 0; i < 500; i++) {
+            n = n.add(r);
+            r = rev(n);
+
+            if (n.equals(r)) {
+                res = new Tuple(false, BigInteger.ZERO);
+                break;
+            }
+
+            if (cache.containsKey(n)) {
+                res = cache.get(n);
+                break;
+            }
+
+            seen.add(n);
+        }
+
+        for (BigInteger bi : seen)
+            cache.put(bi, res);
+
+        return res;
+    }
+
+    public static void main(String[] args) {
+
+        List<BigInteger> seeds = new ArrayList<>();
+        List<BigInteger> related = new ArrayList<>();
+        List<BigInteger> palin = new ArrayList<>();
+
+        for (int i = 1; i <= 10_000; i++) {
+            BigInteger n = BigInteger.valueOf(i);
+
+            Tuple t = lychrel(n);
+
+            if (!t.flag)
+                continue;
+
+            if (n.equals(t.bi))
+                seeds.add(t.bi);
+            else
+                related.add(t.bi);
+
+            if (n.equals(t.bi))
+                palin.add(t.bi);
+        }
+
+        System.out.printf("%d Lychrel seeds: %s%n", seeds.size(), seeds);
+        System.out.printf("%d Lychrel related%n", related.size());
+        System.out.printf("%d Lychrel palindromes: %s%n", palin.size(), palin);
+    }
+}