Safe primes and unsafe primes: Difference between revisions
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There are 74174 unsafe primes below 1000000
There are 633922 unsafe primes below 10000000</pre>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
<syntaxhighlight lang="Delphi">
{Uses seive object that creates an array of flags that tells whether a particular number is prime or not}
function GetSafeUnsafePrimes(MaxCount,MaxPrime: integer; ShowSafe, Display: boolean): string;
{MaxCount = Maximum number of Safe/Unsafe primes to find}
{MaxPrime = Maximum number of primes tested}
{ShowSafe = Controls whether we are looking for Save/Unsafe primes}
{Display = Controls whether the primes are displayed or just counted}
var I,Cnt: integer;
var Sieve: TPrimeSieve;
var IsSafe: boolean;
procedure CountAndDisplay;
begin
Inc(Cnt);
if Display then Result:=Result+Format('%7D',[I]);
If Display and ((Cnt mod 5)=0) then Result:=Result+CRLF;
end;
begin
{Create sieve and set sieve size}
Sieve:=TPrimeSieve.Create;
try
Sieve.Intialize(MaxPrime*2);
Cnt:=0;
Result:='';
I:=2;
while true do
begin
if I>=MaxPrime then break;
IsSafe:=(I>3) and Sieve[(I-1) div 2];
if IsSafe=ShowSafe then CountAndDisplay;
if Cnt>=MaxCount then break;
I:=Sieve.NextPrime(I);
end;
Result:=Result+'Count = '+IntToStr(Cnt);
end;
procedure ShowSafeUnsafePrimes(Memo: TMemo);
var S: string;
begin
Memo.Lines.Add('The first 35 safe primes: ');
S:=GetSafeUnsafePrimes(35,10000000,True,True);
Memo.Lines.Add(S);
Memo.Lines.Add('Safe Primes Under 1,000,000: ');
S:=GetSafeUnsafePrimes(high(integer),1000000,True,False);
Memo.Lines.Add(S);
Memo.Lines.Add('Safe Primes Under 10,000,000: ');
S:=GetSafeUnsafePrimes(high(integer),10000000,True,False);
Memo.Lines.Add(S);
Memo.Lines.Add('The first 40 Unsafe primes: ');
S:=GetSafeUnsafePrimes(40,10000000,False,True);
Memo.Lines.Add(S);
Memo.Lines.Add('Unsafe Primes Under 1,000,000: ');
S:=GetSafeUnsafePrimes(high(integer),1000000,False,False);
Memo.Lines.Add(S);
Memo.Lines.Add('Unsafe Primes Under 10,000,000: ');
S:=GetSafeUnsafePrimes(high(integer),10000000,False,False);
Memo.Lines.Add(S);
end;
</syntaxhighlight>
{{out}}
<pre>
The first 35 safe primes:
5 7 11 23 47
59 83 107 167 179
227 263 347 359 383
467 479 503 563 587
719 839 863 887 983
1019 1187 1283 1307 1319
1367 1439 1487 1523 1619
Count = 35
Safe Primes Under 1,000,000:
Count = 4324
Safe Primes Under 10,000,000:
Count = 30657
The first 40 Unsafe primes:
2 3 13 17 19
29 31 37 41 43
53 61 67 71 73
79 89 97 101 103
109 113 127 131 137
139 149 151 157 163
173 181 191 193 197
199 211 223 229 233
Count = 40
Unsafe Primes Under 1,000,000:
Count = 74174
Unsafe Primes Under 10,000,000:
Count = 633922
Elapsed Time: 700.219 ms.
</pre>
=={{header|F_Sharp|F#}}==
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