How to compare two prime number php?
Hi,
You want to compare two prime number. I am telling you the complete algorithm to compare prime numbers and code snippets in PHP.
Algorithm (From Wikipedia):
1. Create a list of consecutive integers from two to n: (2, 3, 4, …, n),
2. Initially, let p equal 2, the first prime number,
3. While enumerating all multiples of p starting from p2, strike them off from the original list,
4. Find the first number remaining on the list after p (it's the next prime); let p equal this number,
5. Repeat steps 3 and 4 until p2 is greater than n.
6. All the remaining numbers in the list are prime.
Code Snippets:
In this code we have used following Functions.
IsPalindrome
IsInteger
IsEven
IsPositive
IsPerfectSquare
IsPalindromicPrime
<?PHP
function IsInteger($number)
{
$result = preg_match('/^-?[0-9]+$/', $number, $matches);
return $result;
}
function IsEven($number)
{
return (($number % 2) == 0);
}
function IsPositive($number)
{
return $number >= 0;
}
function IsPerfectSquare($number)
{
return sqrt($number) == (int)sqrt($number);
}
function IsPalindrome($number)
{
return $number == strrev($number);
}
function PrimesFromErathosthenes($number)
{
$number = $number + 2; //Otherwise the actual number wouldn't be included in array of numbers
$nlist = array();
$sqrt = ceil(sqrt($number));
$nlist[] = 2;
$nlist[] = 3;
for($i = 5 ; $i < $number ; $i += 2)
{
if($i % 3 != 0)
{
$nlist[] = $i;
}
}
for($i=2,$divisor=5; $divisor < $sqrt ; $i++)
{
$count = count($nlist);
$j = $i*$i;
$nlist2 = array_slice($nlist,0,$j);
for( ; $j < $count ; $j++)
{
$num = $nlist[$j];
if($num % $divisor != 0)
{
$nlist2[] = $num;
}
}
unset($nlist);
$nlist = $nlist2;
$divisor = $nlist[$i+1];
}
$primes = $nlist;
return $primes;
}
function IsPrime($number, $primeSource, $displayOption)
{
if(!IsInteger($number))
{
return false;
}
else
{
$number = (int) $number;
}
if(IsEven($number)){return false;}
$primes;
$IsInPrimesArray = false;
if($primeSource == 'Sieve')
{
$primes = PrimesFromErathosthenes($number);
if(in_array($number, $primes))
{
$IsInPrimesArray = true;
}
else
{
$IsInPrimesArray = false;
}
}
if($primeSource == 'File')
{
$primes = GetFirst100000PrimesFromFile();
$number = "$number"."rn";
if(in_array($number, $primes))
{
$IsInPrimesArray = true;
}
else
{
$IsInPrimesArray = false;
}
}
if($displayOption == 'ShowPrimes')
{
echo "primes ".implode(" ", $primes)."<br />";
}
return $IsInPrimesArray;
}
function IsPalindromicPrime($number, $primeSource, $displayOption)
{
if(!IsPositive($number) || $number > 1318699)
{
return false;
}
if(!IsPalindrome($number))
{
return false;
}
else
{
if(IsPrime($number, $primeSource, $displayOption))
{
return true;
}
else
{
return false;
}
}
}
function GetFirst100000PrimesFromFile()
{
$primes = file('First100000Primes.txt');
return $primes;
}
?>
You can download the code file also. Please Find the attachment.
