Ormiston pairs: Difference between revisions
no edit summary
SqrtNegInf (talk | contribs) (Added Perl) |
No edit summary |
||
Line 459:
Number of Ormiston pairs < 1000000000: 326926
</pre>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
Uses iterator to do both the first 30 and the millionth and 10 millionth pair. It is an easy way to make the same code do both showing a number of pairs and picking counts out of different points in the iteration.
<syntaxhighlight lang="Delphi">
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;
Stop:=Trunc(sqrt(N+0.0));
Result:=False;
while I<=Stop do
begin
if ((N mod I) = 0) or ((N mod (I + 2)) = 0) then exit;
Inc(I,6);
end;
Result:=True;
end;
end;
function GetNextPrime(Start: integer): integer;
{Get the next prime number after Start}
begin
repeat Inc(Start)
until IsPrime(Start);
Result:=Start;
end;
type TPrimeInfo = record
Prime1,Prime2: integer;
Count: integer;
end;
type TOrmIterator = class(TObject)
Info: TPrimeInfo;
private
function IsOrmistonPair(P1, P2: integer): boolean;
protected
public
procedure Reset;
function GetNext: TPrimeInfo;
end;
function TOrmIterator.IsOrmistonPair(P1,P2: integer): boolean;
{Tests if P1 and P2 primes represent Ormiston Pairs}
{I}
var S1,S2: string;
var I,J: integer;
var SL1,SL2: TStringList;
begin
Result:=False;
SL1:=TStringList.Create;
SL2:=TStringList.Create;
try
{Copy characters in numbers into string lists}
SL1.Duplicates:=dupAccept;
SL2.Duplicates:=dupAccept;
S1:=IntToStr(P1); S2:=IntToStr(P2);
for I:=1 to Length(S1) do SL1.Add(S1[I]);
for I:=1 to Length(S2) do SL2.Add(S2[I]);
{Sort them }
SL1.Sort; SL2.Sort;
{And compare them item for item - any mismatch = not Ormiston Pair }
for I:=0 to Min(SL1.Count,SL2.Count)-1 do
if SL1[I]<>SL2[I] then exit;
Result:=True;
finally Sl1.Free; SL2.Free; end;
end;
procedure TOrmIterator.Reset;
{Restart iterator}
begin
Info.Count:=0;
Info.Prime1:=1; Info.Prime2:=3;
end;
function TOrmIterator.GetNext: TPrimeInfo;
{Iterate to next Ormiston Pair}
begin
while true do
begin
Info.Prime2:=GetNextPrime(Info.Prime1);
if IsOrmistonPair(Info.Prime1,Info.Prime2) then
begin
Inc(Info.Count);
Result:=Info;
Info.Prime1:=Info.Prime2;
break;
end
else Info.Prime1:=Info.Prime2;
end;
end;
procedure ShowOrmistonPairs(Memo: TMemo);
var I: integer;
var S: string;
var OI: TOrmIterator;
var Info: TPrimeInfo;
begin
{Create iterator}
OI:=TOrmIterator.Create;
try
OI.Reset;
{Iterate throug 1st 30 pairs}
for I:=1 to 30 do
begin
Info:=OI.GetNext;
S:=S+Format('(%6D %6D) ',[Info.Prime1,Info.Prime2]);
If (Info.Count mod 3)=0 then S:=S+CRLF;
end;
Memo.Lines.Add(S);
Memo.Lines.Add('Count='+IntToStr(Info.Count));
{iterate to millionth pair}
repeat Info:=OI.GetNext
until Info.Prime2>=1000000;
Memo.Lines.Add('1000,000 ='+IntToStr(Info.Count-1));
{iterate to 10 millionth pair}
repeat Info:=OI.GetNext
until Info.Prime2>=10000000;
Memo.Lines.Add('10,000,000 ='+IntToStr(Info.Count-1));
finally OI.Free; end;
end;
</syntaxhighlight>
{{out}}
<pre>
( 1913 1931) ( 18379 18397) ( 19013 19031)
( 25013 25031) ( 34613 34631) ( 35617 35671)
( 35879 35897) ( 36979 36997) ( 37379 37397)
( 37813 37831) ( 40013 40031) ( 40213 40231)
( 40639 40693) ( 45613 45631) ( 48091 48109)
( 49279 49297) ( 51613 51631) ( 55313 55331)
( 56179 56197) ( 56713 56731) ( 58613 58631)
( 63079 63097) ( 63179 63197) ( 64091 64109)
( 65479 65497) ( 66413 66431) ( 74779 74797)
( 75913 75931) ( 76213 76231) ( 76579 76597)
Count=30
1000,000 =382
10,000,000 =3722
Elapsed Time: 10.046 Sec.
</pre>
=={{header|F_Sharp|F#}}==
| |||