Project Euler (APL)

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This is an attempt to learn APL. }:)

Problems

1. Multiples of 3 or 5

⎕IO←1
+/⍸∨⌿0=3 5∘.|⍳999
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2. Even Fibonacci

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first terms will be 1, 2, 3, 5, 8, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms. 

{+/⍵[⍸~2|⍵]}({⍵,+/¯2↑⍵}⍣{4e6<¯1↑⍵})0 1
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3. Largest prime factor

The prime factors of 13 915 are 5, 7, 13, and 29.

What is the largest prime factor of 600 851 475 143? 

f←{⍺←2⋄(⍺×⍺)>⊃⍵:⊃⍵⋄0=⍺|⊃⍵:⍺∇((⊃⍵)÷⍺),⍺,1↓⍵⋄({2=⍵:3⋄⍵+2}⍺)∇⍵}
f 600851475143
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4. Largest palindrome product

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 91 × 99.

Find the largest palindrome made from the product of two 3-digit numbers.

First solution

I wrote this before learning I could use Format (⍕) in place of d. 

⎕IO←0
d←{⍵<10:⍵⋄(∇⌊⍵÷10),(10|⍵)}
p←{{∧/=⌿↑⍵ (⌽⍵)}d⍵}
{{⌈/⍵[⍸p¨⍵]}⍵∘.×⍵}100+⍳899
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Second solution

⎕IO←0
p←{{∧/=⌿↑⍵(⌽⍵)}⍕⍵}
{⌈/⍵[⍸p¨⍵]}∘.×⍨100+⍳899 ⍝ 10+⍳89
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5. Smallest Multiple

2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.

What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?

Using the built-in LCM function

This is a bit too easy. }:P 

⎕IO←1
∧/⍳20
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Handmade LCM

⍝ Modified from function used in the "Largest Prime Factor"
⍝ problem.
f←{⍺←2⋄(⍺×⍺)>⊃⍵:⍵⋄0=⍺|⊃⍵:⍺∇((⊃⍵)÷⍺),⍺,1↓⍵⋄({2=⍵:3⋄⍵+2}⍺)∇⍵}

uhhhh longest mountain pass lol

https://www.codewars.com/kata/660595d3bd866805d00ec4af

References