Data update

Task/Iterated-digits-squaring/PascalABC.NET/iterated-digits-squaring.pas

@@ -0,0 +1,48 @@
+function digits(n: integer): sequence of integer;
+begin
+  result := new List<integer>;
+  repeat
+    result := result + n mod 10;
+    n := n div 10;
+  until n = 0;
+end;
+
+function gen(n: integer): integer;
+begin
+  result := n;
+  while (result <> 1) and (result <> 89) do
+  begin
+    var s := 0;
+    foreach var d in digits(result) do s += d * d;
+    result := s;
+  end;
+end;
+
+function chainsEndingWith89(ndigits: integer): int64;
+begin
+  var prevcount := new Dictionary<integer, int64>;
+  var currcount := new Dictionary<integer, int64>;
+  for var i := 0 to 9 do prevcount[i * i] := 1;
+
+  loop ndigits - 1 do
+  begin
+    currcount.Clear;
+    foreach var prev in prevcount do
+      for var newdigit := 0 to 9 do
+      begin
+        var nextgen := newdigit * newdigit + prev.key;
+        currcount[nextgen] := currcount.get(nextgen) + prev.value;
+      end;
+    prevcount := new Dictionary<integer, int64>(currcount);
+  end;
+
+  foreach var curr in currcount do
+    if (curr.key <> 0) and (gen(curr.key) = 89) then
+      result += curr.value;
+end;
+
+begin
+  println('For  8 digits: ', chainsEndingWith89(8));
+  println('For 18 digits: ', chainsEndingWith89(18));
+  println(milliseconds, 'ms');
+end.