Data commit

Task/Hailstone-sequence/Dart/hailstone-sequence.dart

@@ -0,0 +1,41 @@
+import 'package:collection/collection.dart';
+import 'dart:collection';
+List<int> hailstone(int n) {
+  if(n <= 0) {
+    throw ArgumentError("start value must be >=1)");
+  }
+  var seq = Queue<int>();
+  seq.add(n);
+  while(n != 1) {
+    n = n%2 == 0 ? n ~/ 2 : 3 * n + 1;
+    seq.add(n);
+  }
+  return seq.toList();
+}
+
+main() {
+  for(int i = 1; i <= 10; i++) {
+    print("h($i) = ${hailstone(i)}");
+  }
+  var h27 = hailstone(27);
+  var first4 = h27.take(4).toList();
+  print("first 4 elements of h(27): $first4");
+  assert(ListEquality().equals([27, 82, 41, 124], first4));
+
+  var last4 = h27.skip(h27.length - 4).take(4).toList();
+  print("last 4 elements of h(27): $last4");
+  assert(ListEquality().equals([8, 4, 2, 1], last4));
+
+  print("length of sequence h(27): ${h27.length}");
+  assert(112 == h27.length);
+
+  int seq = 0, max = 0;
+  for(int i = 1; i <= 100000; i++) {
+    var h = hailstone(i);
+    if(h.length > max) {
+      max = h.length;
+      seq = i;
+    }
+  }
+  print("up to 100000 the sequence h($seq) has the largest length ($max)");
+}