euler

I figure it's about time I posted another Project Euler.Problem #30: ∇Z←PETHIRTY;M [1] ⍝ Find the sum of all the numbers that can be written as [2] ⍝ the sum of fifth powers of their decimal digits. [3] Z←+/1↓((⍳M)

Problem #29:∇Z←PETWENTYNINE;⎕IO ⎕IO←1 ⍝ Compute the cardinality of the set ⍝ {a*b | 2≤a≤100 ^ 2≤b≤100} ⍝ Easy to do by computing the sequence, ⍝ ordering it, and then removing duplicates. Z←⍴(-1⌽1↓(Z≠-1⌽Z),1)/Z←Z[⍋Z←

Problem #28:Z←PETWENTYEIGHT ⍝ Sum of the diagonals of a 1001 by 1001 spiral Z←+/+1,4/2×⍳500 This one is too easy to talk about. Basically, we can realize the nature of the spiral and the diagonals is easy to think about

Problem #27:∇Z←PETWENTYSEVEN;A;B;X;P ⍝ Find the product of the coefficients A and B ⍝ that have the longest consecutive n values from 0 ⍝ for the quadratic formula. ⍝ P is the prime table used by CONS∆PRMS. ⍝ Seed it with the primes

Problem #26:∇Z←CYCLE∆LENGTH N;A;I;R ⍝ Find the length of the cycle of 1÷N. Z←0 ⋄ I←0 ⋄ A←N⍴0 ⋄ R←1 LP:I←I+1 ⋄ Z←I-A[R] ⋄ →(0≠A[R])/0 A[R]←I ⋄ R←N|R×

Problem #25:∇R←PETWENTYFIVE;I;A;X;⎕IO;B;D ⎕IO←1 ⍝ What is the first fibonnacci term to contain 1,000 digits? D←1000000000 ⍝ Use nine-digit numbers. A←B←X←¯112↑1 ⍝ Need 112 9-digit numbers to get 1,000 digits. I←2

Problem #24:∇R←PETWENTYFOUR;N;A;I ⍝ Compute the 1,000,000th Lexicographic Permutation of ⍝ 0 through 9. N←10 →(N≥3 2 1)/C3,C2,C1 R←1 0⍴0 ⋄ →0 C1:R←1 1⍴⎕IO ⋄ →0 C2:R←2 2⍴⎕IO+0

Problem #23:∇R←PETWENTYTHREE;ABDP;N;X ⍝ Find the sum of all the positive integers ⍝ which cannot be written as the sum ⍝ of two abundant numbers. ⊣⎕FX 'R←ABDP N' 'R←N<+/(0=(⍳N-1)|N)/⍳N-1' R←+/(~N∊X∘.+X←(ABDP¨N)/N)

Problem 22:∇R←PETWENTYTWO NAMES;X ⍝ Receiving a 1×N matrix of name vectors, ⍝ sort the names alphabetically, and then compute the ⍝ total of their numeric counts times their sorted ⍝ positions. R←+/(⍳↑⍴X)×+/X×~((⍴X)⍴27)=X←⎕AV[97+⍳26]⍳X[⍋X;]⊣X←⊃NAMES[

I didn't really have a good idea of how to solve this one until I started playing around with some things on the APL session. Actually, what do you call the APL REPL, anyways?At any rate, it turned out to be

You notice that these are not daily anymore. :)For this one, I took advantage of the ability to rotate vectors to get the job done. I am confused about the use of the bracket indexing though, and I do not quite understand why I

This one I did the old fashioned way at first, with a loop and a lot of cases and branching. Either with branch arrows or with Control Structures, it felt wrong. In the end, I realized that I could condense things down a bit

For this problem, I could have reused my CARRY function from before, but it seemed like it would only make things more difficult. Instead, I realized that there was a really simple carry algorithm that I could use for this problem. I also did

This was a problem to find all of the forward searching paths in a 20 by 20 grid. This is one that we actually use a lot in our introductory programming courses, but I did not want to do it the way that we

This problem was interesting in all different ways. It asks for Collatz Sequence counts. First, I tried to do the naive way, and discovered how that won't work. I then tried to find a more sophisticated algorithm, and realized that I wouldn&

So, this is actually my post for Friday, but since I was traveling, I was not able to post anything for that day.This one was pretty fun. The problem is that the input to the incoming function was a series of 100 50-digit

This was the first problem that I had to deal with that didn't work right or quickly if I used the standard operators the way that I was used to using them. Instead, I had to create some helper functions that made

I really liked doing this one. I had no idea how to approach this idea at first. I couldn't think of any simple approach to it at all. I decided to look at the APLX Scrapbook and see if I could glean

This was a bit of a fun one, since I had trouble trying to get the result into a 32-bit integer. I had to do a bit of math to get that to work. This one I did a while back, actually, so I

Finally, we get an interesting one. In this problem, I struggled with a desire to express the solution simply, and to also make it computable in a reasonable amount of time. To make things worse, the simplest approach also uses the most memory. I

Again, this problem was just too easy. I wonder why this one was even given actually, because in something like Scheme, this would also be very easy.Anyways, here it is. Nothing fancy here:∇R←PEEIGHT;S S←'73167176531330624919225119674426574742355349194934' S←S,'

Nothing much to say about this one. I use the basic prime sieve on this one. I am still playing with whether I like branch arrows or control structures better.∇R←PESEVEN;X;N;⎕IO ⎕IO←1 ⍝ The 10001st prime number. N←150000 ⋄ X←

This one was too easy, I probably am doing it wrong.R←PESIX;⎕IO ⎕IO←1 ⍝ Difference between the sum of the squares of the first ⍝ 100 natural numbers and the square of the sum of the same. R←((+/⍳100)*2)-+/(⍳100)*2

I really do not like my solution here, but it was the simplest at the time. I think that there is definitely a neater way to do this one:Problem #5:R←PEFIVE ⍝ What is tthe smallest positive number that is evenly divisible ⍝ by