Puzzle 8-13-2008 (answers)

[Steven Schveighoffer]

"BCS" wrote
> Reply to Steven,
>> void prob2()
>> {
>> auto target= 600_851_475_143;
>> for(ulong i = 3; i * i < target; i++)
>> if(target % i == 0)
>> {
>> Stdout(i).newline;
>> return;
>> }
>> Stdout(target)(" is prime!").newline;
>> }
>
> doesn't that find the smallest factor?

Correction, smallest *prime* factor (which is also the smallest factor) :) 
Of course, I now realize that I misread the question...

Quick change to my code:

void prob2()
{
    auto target= 600_851_475_143;
    for(ulong i = 3; i * i <= target; i++)
        while(target % i == 0)
        {
            target /= i;
        }
    Stdout(target).newline;
}

New answer to 2:

6857

new times (pretty much the same):

real    0m0.004s
user    0m0.003s
sys     0m0.001s

-Steve