Pandigital prime: Difference between revisions
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0..7: 76,540,231 24.5 μs</pre>
=={{header
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
The original version generated results that weren't prime. This version has been rewritten to fix the prime problem and make it more modular.
<syntaxhighlight lang="Delphi">
{This code is normally put in a separate library, but it is included here for clarity}
function IsPrime(N: int64): boolean;
{Fast, optimised prime test}
var I,Stop: int64;
begin
if (N = 2) or (N=3) then Result:=true
else if (n <= 1) or ((n mod 2) = 0) or ((n mod 3) = 0) then Result:= false
else
begin
I:=5;
while I<=Stop do
if ((N mod I) = 0) or ((N mod (I + 2)) = 0) then exit;
Inc(I,6);
end;
Result:=True;
end;
end;
function HighestPandigitalPrime(ZeroBased: boolean): integer;
{Returns the highest pandigital prime}
{ZeroBased = includes 0..N versus 1..N }
var I: integer;
type TDigitFlagArray = array [0..9] of integer;
procedure GetDigitCounts(N: integer; var FA: TDigitFlagArray);
{Get a count of all the digits in the number}
var T,I,DC: integer;
begin
DC:=Trunc(Log10(N))+1;
{Zero counts}
for I:=0 to High(FA) do FA[I]:=0;
{Count each time a digits is used}
for I:=0 to DC-1 do
begin
T:=N mod 10;
N:=N div 10;
Inc(FA[T]);
end;
end;
function IsPandigital(N: integer): boolean;
{Checks to see if all digits 0..N or 1..N are included}
var IA: TDigitFlagArray;
var I,DC: integer;
var Start: integer;
begin
Result:=False;
{ZeroBased includes zero}
if ZeroBased then Start:=0 else Start:=1;
{Get count of digits}
DC:=Trunc(Log10(N))+1;
{Get a count of each digits that are used}
GetDigitCounts(N,IA);
{Each digit 0..N or 1..N can only be used once}
for I:=Start to DC-1 do
if IA[I]<>1 then exit;
Result:=True;
end;
begin
if ZeroBased then Result:=76543210+1 else Result:=7654321;
{Check all numbers in the range}
while Result>2 do
begin
{Check that number is prime and Pandigital}
if IsPrime(Result) then
if IsPandigital(Result) then break;
Dec(Result,2);
end;
end;
procedure PandigitalPrime(Memo: TMemo);
var P: integer;
begin
P:=HighestPandigitalPrime(False);
Memo.Lines.Add(Format('Non Zero Based: %11.0n',[P+0.0]));
P:=HighestPandigitalPrime(True);
Memo.Lines.Add(Format('Zero Based: %11.0n',[P+0.0]));
end;
</syntaxhighlight>
{{out}}
<pre>
Non Zero Based: 7,652,413
Zero Based: 76,540,231
Elapsed Time: 6.044 ms.
</pre>
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