Largest difference between adjacent primes: Difference between revisions
Largest difference between adjacent primes (view source)
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Largest gap between primes under 10,000,000,000 is 354.
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=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
<syntaxhighlight lang="Delphi">
function IsPrime(N: integer): boolean;
{Optimised prime test - about 40% faster than the naive approach}
var I,Stop: integer;
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));
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;
procedure LargestPrimeDifference(Memo: TMemo);
{Find the largest difference between primes under 1 million}
var I: integer;
var P1,P2: integer;
var Delta,Largest,Prime1,Prime2: integer;
begin
Largest:=0;
P1:=1;
for I:=1 to 1000000-1 do
if IsPrime(I) then
begin
Delta:=I - P1;
if Delta>Largest then
begin
Largest:=Delta;
Prime1:=P1;
Prime2:=I;
end;
P1:=I;
end;
Memo.Lines.Add(Format('Prime1: %d Prime2: %d Diff: %d',[Prime1,Prime2,Largest]));
end;
</syntaxhighlight>
{{out}}
<pre>
Prime1: 492113 Prime2: 492227 Diff: 114
</pre>
=={{header|F_Sharp|F#}}==
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