Data commit

Task/Hailstone-sequence/Elena/hailstone-sequence.elena

@@ -0,0 +1,50 @@
+import system'collections;
+import extensions;
+
+const int maxNumber = 100000;
+
+Hailstone(int n,Map<int,int> lengths)
+{
+    if (n == 1)
+    {
+        ^ 1
+    };
+
+    while (true)
+    {
+        if (lengths.containsKey(n))
+        {
+            ^ lengths[n]
+        }
+        else
+        {
+            if (n.isEven())
+            {
+                lengths[n] := 1 + Hailstone(n/2, lengths)
+            }
+            else
+            {
+                lengths[n] := 1 + Hailstone(3*n + 1, lengths)
+            }
+        }
+    }
+}
+
+public program()
+{
+    int longestChain := 0;
+    int longestNumber := 0;
+    auto recursiveLengths := new Map<int,int>(4096,4096);
+
+    for(int i := 1, i < maxNumber, i+=1)
+    {
+        var chainLength := Hailstone(i, recursiveLengths);
+        if (longestChain < chainLength)
+        {
+               longestChain := chainLength;
+               longestNumber := i
+        }
+    };
+
+    console.printFormatted("max below {0}: {1} ({2} steps)", maxNumber, longestNumber, longestChain)
+}