[Blindmath] new member... with a question!

[Alastair Irving]

Hi

The question of how to solve the problem is rather off topic for this 
list, but the question of where to find accessible materials is not.

The two sites I would start with are wikipedia and mathworld.  Both of 
these use images for equations but the alt-tag is in LaTeX so can be 
read with a screenreader.  (Even if you're not familiar with LaTeX it 
should be reasonably obvious what most things mean, ^ for superscript 
and _ for subscript, etc).

Both sites have articles on all the common integer factorisation 
algorithms.  However, I actually don't think they're needed in this 
case.  The number is less than 2^64 so you should be able to solve the 
problem in any language with a 64-bit integer type.  I actually just 
solved it using python, and the time taken was very small.

HTH

Alastair Irving



Alex Hall wrote:
> Hi all,
> My name is Alex. I am in college for computer science, in my third year. In 
> reading the description of this list I realize that the below is not quite 
> in keeping with the usual topics on this list, however I am hoping that 
> someone on here can point me to a list which would better suit my question. 
> Here goes...
> 
> I am working on the problems at http://www.projecteuler.net and am on 
> problem 3, which asks for the highest prime factor of some very large number 
> (over six hundred billion). I am writing a small program to give me the 
> answer, however the number is too large to (A) be stored in the usual 
> variable type or (B) return an answer in anything approaching a fast time 
> (if I use the old "try them all" method by dividing every number up to n/2 
> into n and seeing if the result is 0, my time will be n/2-2). I tried 
> getting the square and factoring that, but the square is a decimal that 
> looks infinite. I know some numbers lend themselves to being prime-factored 
> by getting the square root of the square above the number then finding the 
> gcf of the number and the square root +1 and minus 1, but this does not work 
> for all numbers and I am not sure what the trick to figuring out if it will 
> work or not is.
> So... is there a fast (ish) way to factor some number that is well over 
> three hundred billion? I use JAWS, so an explanation in words supported by 
> math, instead of all math symbols, would be great. As I said at the 
> beginning of this message, I expect that this question is not what this list 
> is for, but I hope that asking it will tell people what kind of list I am 
> looking for and, if they know of one, they can tell me what it is. Thanks 
> for any help!
> 
> 
> Have a great day,
> Alex
> New email address: mehgcap at gmail.com 
> 
> 
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