<?php
include_once 'primefunctions.php';
$input = $_POST['input'];
$title = "Prime factors of {$input}";
include_once 'header.php';
echo "<center><h1>{$title}</h1>";
if ($input > 100000) {
echo "Less of the huge numbers, you! Let's keep it below 100,000 for everyone's sake";
} else {
$i = 0;
$factors = prime_factors($input);
foreach ($factors as $factor) {
echo "{$factor} ";
$i++;
if ($i == 5) {
$i = 0;
echo "<br />";
}
}
}
echo "<p><a href='index.php'>Return to main page</a></p>";
<?php
$t = array();
for ($i = 2; $i <= 20; $i++) {
$pfs = prime_factors($i);
foreach ($pfs as $pf => $pfpow) {
if ($t[$pf] < $pfpow) {
$t[$pf] = $pfpow;
}
}
}
print_r($t);
// return an array where the key is the prime factor and the value the power
function prime_factors($num)
{
$results = array();
for ($f = 2; $f <= $num; $f++) {
$exp = 1;
while (fmod($num, $f) == 0) {
$num = $num / $f;
$results["{$f}"] = $exp++;
}
}
return $results;
}
<?php
// the number of divisors of an integer d(n) can be obtained
// doing a prime factorization.
// just add 1 to every factor's exponent and multiply them
// Ex. 36 = (2^2) * (3^2) = 3 * 3 = 9
// 28 = (2^2) * (7^1) = 3 * 2 = 6
$t = 1;
$div = 1;
while ($div < 500) {
$num = $num + $t;
// triangle number
$pf = prime_factors($num);
$div = array_reduce($pf, 'mulplus1', 1);
// apply mulplus1() to every element of the array
echo "{$t} {$num} {$div}\n";
$t++;
}
// return an array where the key is the prime factor and the value the power
function prime_factors($num)
{
$results = array();
for ($f = 2; $f <= $num; $f++) {
$exp = 1;
while (fmod($num, $f) == 0) {
$num = $num / $f;
$results["{$f}"] = $exp++;
}
}
return $results;
}
<?php
require_once './model/model.php';
$ttime = microtime(true);
$stime = microtime(true);
$below = 600851475143;
$problem = <<<'XXX'
Largest prime factor<br><br>
Problem 3<br>
The prime factors of 13195 are 5, 7, 13 and 29.<br>
<br>
What is the largest prime factor of the number 600851475143 ?<br>
source: https://projecteuler.net/problem=3 <br>
XXX;
//Title
echo $problem;
echo "<br>";
//Method 1 - Recursion
start_method();
$lpf = prime_factors($below);
end_method();
result("recursive", "largest prime factor of the number {$below}", $lpf, "1", $stime);
//Method 2 - Haskell
start_method();
$lpf = prime_factors_haskell($below);
end_method();
result("recursive haskell", "largest prime factor of the number {$below}", $lpf, "2", $stime);
echo "Total time of php execution was " . (microtime(true) - $ttime) . " seconds <br>";
