# Thread: [PE] - Project Euler club

1. ## Re: [PE] - Project Euler club

That's one of the reasons I kind of wanted to start this thread. There are very elegant ways to solve these problems and there are very ugly ways to solve these problems. For the first page or two it's fairly easy to come up with SOME solution but it might not be the prettiest thing. There aren't too many people on PE that use R to solve the problems so I wanted to see if a group of people would offer up solutions (pretty or ugly - I like to see both) coded in R. Some of them like I said don't even need programming but even for the ones that we can come up with an analytic solution for can have some nice code to do the job as well.

2. ## Re: [PE] - Project Euler club

Problem 79:
A common security method used for online banking is to ask the user for three random characters from a passcode. For example, if the passcode was 531278, they may ask for the 2nd, 3rd, and 5th characters; the expected reply would be: 317.
The text file, keylog.txt, contains fifty successful login attempts.
Given that the three characters are always asked for in order, analyse the file so as to determine the shortest possible secret passcode of unknown length.
Spoiler:

3. ## Re: [PE] - Project Euler club

Problem 67

By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23.

3
7 4
2 4 6
8 5 9 3

That is, 3 + 7 + 4 + 9 = 23.

Find the maximum total from top to bottom in triangle.txt (right click and 'Save Link/Target As...'), a 15K text file containing a triangle with one-hundred rows.

NOTE: This is a much more difficult version of Problem 18. It is not possible to try every route to solve this problem, as there are 299 altogether! If you could check one trillion (1012) routes every second it would take over twenty billion years to check them all. There is an efficient algorithm to solve it. ;o)

Hint:
Spoiler:

My solution:
Spoiler:

4. ## Re: [PE] - Project Euler club

And if somebody wants to PM the username and password... I kind of forgot them. I'm pretty sure the account is under my email address so I could reset the password but I don't want to lock anybody else out. I used my personal PE account to do that last one but I would like to get the TS account credit for it.

Edit: Thanks Jake!

Also - I went and did #18 because it's the same exact problem except smaller. The idea there was that you actually can brute force the solution for #18 but it would take FOREVER to bruteforce #67.

5. ## Re: [PE] - Project Euler club

Some really cool R programming. Natty! My level of R programming is next to nothing. But hey, anything that helps me improve my R skills, I'll jump into. I'll be interested in PE.Count me in (but don't expect anything from me though). What takes you 5 mins to solve will keep me reeling for weeks if not months!

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