Data commit

Task/Executable-library/Java/executable-library-1.java

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+import java.util.ArrayList;
+import java.util.List;
+
+//  task 1
+public class HailstoneSequence {
+
+    public static void main(String[] args) {
+        //  task 2
+        int n = 27;
+        List<Long> sequence27 = hailstoneSequence(n);
+        System.out.printf("Hailstone sequence for %d has a length of %d:%nhailstone(%d) = %s%n", n, sequence27.size(), n, sequence27);
+
+        //  task 3
+        int maxN = 0;
+        int maxLength = 0;
+        for ( int i = 1 ; i < 100_000 ; i++ ) {
+            int seqLength = hailstoneSequence(i).size();
+            if ( seqLength > maxLength ) {
+                maxLength = seqLength;
+                maxN = i;
+            }
+        }
+        System.out.printf("Longest hailstone sequence less than 100,000: hailstone(%d).length() = %d", maxN, maxLength);
+    }
+
+    public static List<Long> hailstoneSequence(long n) {
+        if ( n <= 0 ) {
+            throw new IllegalArgumentException("Must be grater than or equal to zero.");
+        }
+        List<Long> sequence = new ArrayList<>();
+        sequence.add(n);
+        while ( n > 1 ) {
+            if ( (n & 1) == 0 ) {
+                n /= 2;
+            }
+            else {
+                n = 3 * n + 1;
+            }
+            sequence.add(n);
+        }
+        return sequence;
+    }
+
+}

Task/Executable-library/Java/executable-library-2.java

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+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.IntStream;
+
+public class ExecutableLibrary {
+
+    public static void main(String[] args) {
+        Map<Integer,Integer> lengthMap = new HashMap<>();
+        IntStream.range(1, 100_000)
+                 .map(n -> HailstoneSequence.hailstoneSequence(n).size())
+                 .forEach(len -> lengthMap.merge(len, 1, (v1, v2) -> v1 + v2));
+        int mostOften = lengthMap.values()
+                                 .stream()
+                                 .mapToInt(x -> x)
+                                 .max().orElse(-1);
+
+        System.out.printf("The most frequent hailstone length for n < 100,000 is %d.%n", mostOften);
+    }
+
+}