Data commit

Task/Untouchable-numbers/Delphi/untouchable-numbers.delphi

@@ -0,0 +1,123 @@
+program Untouchable_numbers;
+
+{$APPTYPE CONSOLE}
+
+uses
+  System.SysUtils;
+
+function SumDivisors(n: Integer): Integer;
+begin
+  Result := 1;
+  var k := 2;
+  if not odd(n) then
+    k := 1;
+  var i := 1 + k;
+  while i * i <= n do
+  begin
+    if (n mod i) = 0 then
+    begin
+      inc(Result, i);
+      var j := n div i;
+      if j <> i then
+        inc(Result, j);
+    end;
+    inc(i, k);
+  end;
+end;
+
+function Sieve(n: Integer): TArray<Boolean>;
+begin
+  inc(n);
+  SetLength(result, n + 1);
+  for var i := 6 to n do
+  begin
+    var sd := SumDivisors(i);
+    if sd <= n then
+      result[sd] := True;
+  end;
+end;
+
+function PrimeSieve(limit: Integer): TArray<Boolean>;
+begin
+  inc(limit);
+  SetLength(result, limit);
+  Result[0] := True;
+  Result[1] := True;
+
+  var p := 3;
+  repeat
+    var p2 := p * p;
+    if p2 >= limit then
+      Break;
+    var i := p2;
+    while i < limit do
+    begin
+
+      Result[i] := True;
+      inc(i, 2 * p);
+    end;
+
+    repeat
+      inc(p, 2);
+    until not Result[p];
+
+  until (False);
+
+end;
+
+function Commatize(n: Double): string;
+var
+  fmt: TFormatSettings;
+begin
+  fmt := TFormatSettings.Create('en-US');
+  Result := n.ToString(ffNumber, 64, 0, fmt);
+end;
+
+begin
+  var limit := 1000000;
+  var c := primeSieve(limit);
+  var s := sieve(63 * limit);
+  var untouchable: TArray<Integer> := [2, 5];
+  var n := 6;
+  while n <= limit do
+  begin
+    if not s[n] and c[n - 1] and c[n - 3] then
+    begin
+      SetLength(untouchable, Length(untouchable) + 1);
+      untouchable[High(untouchable)] := n;
+    end;
+    inc(n, 2);
+  end;
+  writeln('List of untouchable numbers <= 2,000:');
+  var count := 0;
+  var i := 0;
+  while untouchable[i] <= 2000 do
+  begin
+    write(commatize(untouchable[i]): 6);
+    if ((i + 1) mod 10) = 0 then
+      writeln;
+    inc(i);
+  end;
+  writeln(#10#10, commatize(count): 7, ' untouchable numbers were found  <=     2,000');
+
+  var p := 10;
+  count := 0;
+  for n in untouchable do
+  begin
+    inc(count);
+    if n > p then
+    begin
+      var cc := commatize(count - 1);
+      var cp := commatize(p);
+      writeln(cc, ' untouchable numbers were found  <= ', cp);
+      p := p * 10;
+      if p = limit then
+        Break;
+    end;
+  end;
+
+  var cu := commatize(Length(untouchable));
+  var cl := commatize(limit);
+  writeln(cu:7, ' untouchable numbers were found  <= ', cl);
+  readln;
+end.