Project Euler Forum

I am planning to discuss several problems of Project Euler in my blog. It's written in Indonesian.
My main problem is i don't know where the "border" is.

I know exactly that i must not publish anything close to solution. Hence i write down something more conceptual.
Let's consider PE Problem#1 as an example. When i discuss this problem, i - of course - didn't publish the exact solution. Instead, i write another topic close to it. Such as arithmetic series. I know exactly that all high school in my country teaches it. So i just 'refresh' my visitor's mind by talking about it. I argue that this kind of post/discussion doesn't break anything in Project Euler spirits.

Furthermore, i even extend PE Problem#1 to a harder one. This - i believe - matches Project Euler spirits. By extending PE Problem#1, the discussion on my blog goes to another topic, which is Inclusion-Exclusion Principle. This kind of topic is never discussed in any high school in my country. This way, i realize that i have participated on building/encouraging/supporting/developing education in my country.

Now, will somebody clarify me 'what can' and 'what cannot' be written down in one's personal blog? Without breaking Project Euler spirit and within the spirit of encouraging the education itself.

This is a nice question that is of current interest that deserves general discussion to crystallise out.

So let's fire off some thoughts for others to shoot down.
I think this depends very much on the particular Project Euler problem.
Some of them are rather specific for PE others are of a more general type.
Let's take Problem 10 (View Problem).
If one writes up a nice article about primesieves without mentioning that this concerns PE#10 could anyone be accused of spoiling PE#10? I don't think so. Even if you provide sourcecode for a primesieve.
What certainly is across the border in my opinion, (but that is my personal opinion) is a set of write ups about a lot of consecutive PE problems, with their problem number mentioned, including sourcecode. This would enable others to thoughtlessly run the code and fill in the answer on PE (and thus wouldn't have learned anything)
So ask yourself: makes my blog entry it possible for someone else to fill in the answer on PE without doing more than copy the code given (or to translate the pseudocode into one's favorite programming language).
In general I would say: someone reading your blog should have to do quite something to
1) identify that this concerns PE problem xxx, and/or
2) translate the information given into a working program that provides the answer to the PE problem in question.
But perhaps others have another view about things.

Often, I don't even have the slightest clue how to solve a PE problem. For example, I don't know what Markov chains are and what they are good for (although I might now know if I need them, after having seen them used in one particular PE problem forum).

So let's suppose I stumble upon your blog and it says: "To solve problem xyz, you need to use Markov chains!" - that'd allow me to just read up what they are and hopefully solve the problem.

I'm not sure if that is what PE is meant to be about. Maybe I should think about the problem until I find a solution that works, even without knowing what a Markov chain is, or until I find out what Markov chains are without you telling me that I need them for this particular problem.

I have solved quite some problems in a way that is not the most obvious way to approach them, because I didn't know about that obvious way.
For example, I remember a problem that asked for a way through a square of numbers with the sum of all used numbers minimized, or something like that. In the problem thread, most people used Dynamic Programming, and I didn't know about Dynamic Programming back then. But I did know the A* Algorithm for finding shortest paths and so I used A* to solve it.

If all I had to do to find the "straight-forward" way to solve a problem is looking up the PE problem number in your blog, that would surely help me find a solution for some problems that I'm unable to solve now, but it's missing the fun of finding creative ways to solve a problem using the few mathematical skills that I have now.

Just my two cents.

As for my input, I think any mathematical blog out there would fail to be valid if yours isn't, as long as there is no hint to a particular problem, because people who try and use your blog to solve PE problems will have to go through all of the posts, and understand them, and then use the knowledge presented to solve problems. Thus, in my opinion, your blog will not violate any policy I can think of, and moreover, IMHO this is an excellent idea, promoting both your own and others' understanding of mathematics.

Any blog that explicitly gives away the methods, programs and/or insights belonging to PExxx, with an obvious reference to that problem, should be considered unwanted, but I get the impression your blog doesn't fall in this category.

Hi all. Thanks for the inputs.
From several opinions shown, i think this is the raw version of 'what can' and 'what cannot' be written down in one's personal blog :

What Can
- Everything, except

What Cannot
- Giving final solution(s) to any problem. Cheating
- Explicitly announcing that a particular trick/technique/method is useful to solve problem xxx. Spoiling
- Explicitly announcing that a particular pseudo-code/source code solves problem xxx. Almost cheating

The above list of course still open to other's input.
Lol. The 'almost cheating' part reminds me of Problem 94 (View Problem) : "almost equilateral triangle"