aoc-2019/04/main.pony

use "collections"
use "format"
use "itertools"

primitive Password
  fun is_valid_pt1(pass: U64): Bool =>
    let digits: String box = Format.int[U64](pass)
    var pairwise = Array[(U8, U8)]()
    Iter[U8](digits.values()).zip[U8](Iter[U8](digits.values()).skip(1)).collect(pairwise)
    let two_adjacent = Iter[(U8, U8)](pairwise.values()).any({(tup) => (let l, let r) = tup; l == r})
    let increasing = Iter[(U8, U8)](pairwise.values()).all({(tup) => (let l, let r) = tup; l <= r})
    (digits.size() == 6) and two_adjacent and increasing

  fun is_valid_pt2(pass: U64, env: Env): Bool =>
    let digits: String box = Format.int[U64](pass)
    let increasing = Iter[U8](digits.values()).zip[U8](Iter[U8](digits.values()).skip(1)).all({(tup) => (let l, let r) = tup; l <= r})
    var last: U8 = 0
    var this_run: U8 = 0
    var runs = Array[U8]()
    for d in digits.values() do
      if d == last then
        this_run = this_run + 1
      else
        runs.push(this_run)
        this_run = 0
      end
      last = d
    end
    runs.push(this_run)
    let only_one_double = Iter[U8](runs.values()).filter({(n) => n == 1}).count() >= 1
    (digits.size() == 6) and increasing and only_one_double

actor Main
  new create(env: Env) =>
    let valids = Iter[U64](Range[U64](240298, 784956)).filter({(n) => Password.is_valid_pt2(n, env)})
    env.out.print("Valid passwords: " + Format.int[USize](valids.count()))