A-M baby

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

@@ -0,0 +1,52 @@
+List<int> hailstone(int n) {
+  if(n<=0) {
+    throw new IllegalArgumentException("start value must be >=1)");
+  }
+  Queue<int> seq=new Queue<int>();
+  seq.add(n);
+  while(n!=1) {
+    n=n%2==0?(n/2).toInt():3*n+1;
+    seq.add(n);
+  }
+  return new List<int>.from(seq);
+}
+
+// apparently List is missing toString()
+String iterableToString(Iterable seq) {
+  String str="[";
+  Iterator i=seq.iterator();
+  while(i.hasNext()) {
+    str+=i.next();
+    if(i.hasNext()) {
+      str+=",";
+    }
+  }
+  return str+"]";
+}
+
+main() {
+  for(int i=1;i<=10;i++) {
+    print("h($i)="+iterableToString(hailstone(i)));
+  }
+  List<int> h27=hailstone(27);
+  List<int> first4=h27.getRange(0,4);
+  print("first 4 elements of h(27): "+iterableToString(first4));
+  Expect.listEquals([27,82,41,124],first4);
+
+  List<int> last4=h27.getRange(h27.length-4,4);
+  print("last 4 elements of h(27): "+iterableToString(last4));
+  Expect.listEquals([8,4,2,1],last4);
+
+  print("length of sequence h(27): "+h27.length);
+  Expect.equals(112,h27.length);
+
+  int seq,max=0;
+  for(int i=1;i<=100000;i++) {
+    List<int> h=hailstone(i);
+    if(h.length>max) {
+      max=h.length;
+      seq=i;
+    }
+  }
+  print("up to 100000 the sequence h($seq) has the largest length ($max)");
+}