Elegant Euler solutions in Ruby

The basic strategy is to only check to the east, south, southeast and southwest. By checking those we are implicitly checking north, west, northwest and northeast…..

This problem uses a lot of the helper functions we have defined previously. The major changes are:

• We define a “primes” method that returns an array of all primes than that self…..

Not much interesting on this problem. Just brute force trial of numbers 1..999. We do trim the ranges a bit to make it run fast but that is about it.

This one really involves almost more string manipulation than number crunching. Notice how nicely we can get a substring using the brackets. Also notice how chars gives us each character in our substring as something we can enumerate. This means a simple Enumerable helper method to calculate the product (like previous problems did with sum) and the problem become almost a one liner…..

Most of the helper methods are just borrowed from Problem 3. What I like about this problem is that even though often blocks in Ruby provide a unique way of solving a problem you can also use more traditional control structures to express an equally elegant solution…..

This is another one where after defining a few support methods (sum from a previous problems) the actual calculation almost reads exactly as the problem describes.

This problem really doesn’t introduce anything previous problems have shown. But I do love the way I can use a quick block in an if statement combined with all?. Makes something that is a big loop in most languages almost feel like a keyword.

This solution tries to be elegant as possible but I am not in love with two aspects:

• The actual block that calculates the solution seems unnecessarily complex. Is there a way we can abstract some of the logic into generic methods like we did for Problem 3?….

What I like about this solution is that it consists of just adding a few extensions to the Numeric class plus a simple line that almost repeats the problem given. Ruby does actually include a prime generator through the Prime object in the mathn library. But it seemed to perform worse that even my ultra-naive solution to generating the prime numbers…..

Often I need to test some variable against 2 or 3 values. The standard way to do it in most languages is:

This can get ugly if you start using more than 2 conditions (even if it is still a small number such as 3 or 4). Also sometimes your variable is not a variable but a chain of method calls that you don’t want to evaluate every time. For example:….