Question

I am not able to solve the Amazon Interviewstreet challenge for fibonacci factor in php.
https://amazon.interviewstreet.com/challenges/dashboard/#problems

Fibonacci values upto 10^18

large int values seem to be the problem and bcmath is not helping…

My Code –

<?php
function s($k)
{
$x=$y=1;
    while($y<=$k)
    {
    $z=$x+$y;
    $x=$y;
    $y=$z;
        if($y%2==0&&$k%2==0)
            {
                fprintf(fopen("php://stdout", "w"), "%d ", 2);
                fprintf(fopen("php://stdout", "w"), "%d\n", 2);
                return;
            }
    for($i=3;$i<=$y;$i+=2)
            if($y%$i==0&&$k%$i==0)
            {
                fprintf(fopen("php://stdout", "w"), "%d ", $y);
                fprintf(fopen("php://stdout", "w"), "%d\n", $i);
                return;
            }
    }
    while($y%$k!=0)
    {
    $z=$x+$y;
    $x=$y;
    $y=$z;
    }
    fprintf(fopen("php://stdout", "w"), "%d ", $y);
    fprintf(fopen("php://stdout", "w"), "%d\n", $k);   
}
fscanf(STDIN, "%d\n", $t);
while($t--)
{
    fscanf(STDIN, "%d\n", $k);
    s($k);
}
?>

Answer 1

<?php
function s($k)
{
    $e=1;$f=2;
    while($f<=$k)
    {
        $g=$e+$f;
        $e=$f;
        $f=$g;
        for($d=3;$d<=$f;$d+=2)
            if($f%$d==0&&$k%$d==0)
                return $f.' '.$d;
    }
    while(bcmod($f,$k)!=0)
    {
        $g=bcadd($e,$f);
        $e=$f;
        $f=$g;
    }
    return $f.' '.$k;
}

fscanf(STDIN, "%d\n", $t);
while($t--)
{
    fscanf(STDIN, "%d\n", $k);
    if($k%2==0)
        echo '2 2'.PHP_EOL;
    else
        echo s($k).PHP_EOL;
}
?>