## APL Hacking: Project Euler (#30)

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)=+⌿(((1+⌊10⍟M)⍴10)⊤⍳M)*5)

## Revisiting Send + More = Money

In my last post I attempted to solve the Send + More = Money Cryptarithmetic problem. I didn't quite understand how I could do this quickly using a better algorithm, so I tried to find a simple brute force solution. As it turns out, that solution is actually reasonably fast,

## Send + More = Money

After talking with Prof. Friedman, he gave me an interesting constraint problem. This is a well known example of a problem well suited to constrain based techniques. The goal is to figure out what number to assign to each letter to make the equation "send + more = money" true.

## APL Hacking: Project Euler (#29)

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←,(1↓⍳100)∘.*(1↓⍳100)] ∇Another easy

## APL Hacking: Project Euler (#28)

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 without generating the spiral.On the