From bc3c9a0e461a4ba8161732ffe1946a21d89a5195 Mon Sep 17 00:00:00 2001
From: Luna <git@l4.pm>
Date: Sun, 2 Dec 2018 03:04:16 -0300
Subject: [PATCH] add day 2 solutions

---
 day2/day2_1.ex | 69 ++++++++++++++++++++++++++++++++++++++++++++
 day2/day2_2.ex | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 day2/day2_1.ex
 create mode 100644 day2/day2_2.ex

diff --git a/day2/day2_1.ex b/day2/day2_1.ex
new file mode 100644
index 0000000..9d05197
--- /dev/null
+++ b/day2/day2_1.ex
@@ -0,0 +1,69 @@
+input = IO.gets("input?")
+        |> String.trim
+        |> String.split(" ")
+
+defmodule Solver do
+
+  # convert from bool to 1/0
+  def to_num(boolean) do
+    if boolean do
+      1
+    else
+      0
+    end
+  end
+
+  def process(input) do
+    ids_properties = Enum.map(input, fn box_id ->
+
+      # convert string to list
+      box_id_chars = box_id |> String.split("") |> Enum.filter(fn char ->
+        char != ""
+      end)
+
+      # get the letter repeats for each char in it
+      counts = Enum.map(box_id_chars, fn id_letter ->
+
+        count = Enum.count(box_id_chars, fn character ->
+          character == id_letter
+        end)
+
+        count
+      end)
+
+      IO.puts "counts: #{inspect counts}"
+
+      # check if it has letters repeated twice or three times
+      r = {
+        Enum.count(counts, fn count -> count == 2 end) > 1,
+        Enum.count(counts, fn count -> count == 3 end) > 1
+      }
+
+      IO.puts "result: #{inspect r}"
+
+      r
+    end)
+
+    # count all box ids that have twice/three-repeated
+    {total_twice, total_three} = Enum.reduce(ids_properties, {0, 0}, fn property, acc ->
+      {old_twice, old_three} = acc
+      {is_twice, is_three} = property
+
+      change_tw = to_num(is_twice)
+      change_th = to_num(is_three)
+
+      {
+        old_twice + change_tw,
+        old_three + change_th
+      }
+    end)
+
+    # Solution
+    total_twice * total_three
+  end
+
+end
+
+IO.puts "input: #{input}"
+result = Solver.process(input)
+IO.puts "ACTUAL RESULT: #{result}"
diff --git a/day2/day2_2.ex b/day2/day2_2.ex
new file mode 100644
index 0000000..5dfcddb
--- /dev/null
+++ b/day2/day2_2.ex
@@ -0,0 +1,77 @@
+input = IO.gets("input?")
+        |> String.trim
+        |> String.split(" ")
+
+defmodule Solver do
+
+  def to_list(string) do
+    case string do
+      "" -> []
+      _ ->
+        string
+        |> String.split("")
+        |> Enum.filter(fn char ->
+          char != ""
+        end)
+    end
+  end
+
+  # get the common string between the box ids
+  def get_common(box_id, box_id_2) do
+
+    # convert to list
+    box_id_l = to_list(box_id)
+    box_id_2_l = to_list(box_id_2)
+
+    # zip them
+    list_chars = Enum.zip(box_id_l, box_id_2_l)
+
+    # if theyre equal, we add to the accumulator
+    common_str = Enum.reduce(list_chars, "", fn tup, acc ->
+      {c1, c2} = tup
+
+      if c1 == c2 do
+        acc <> c1
+      else
+        acc
+      end
+    end)
+
+    # for common_str to be valid it has to be
+    # L(common_str) = L(box_id) - 1
+    # since correct box ids have just *ONE*
+    # character difference between them
+    if String.length(common_str) == (String.length(box_id) - 1) do
+      {:ok, common_str}
+    else
+      :not_found
+    end
+
+  end
+
+  def solve(input) do
+    # find all the common strings
+    # and filter shit
+    commons = Enum.map(input, fn box_id ->
+      Enum.map(input, fn box_id_2 ->
+        common = get_common(box_id, box_id_2)
+
+        case common do
+          :not_found -> nil
+          {:ok, str} -> str
+        end
+      end)
+      |> Enum.filter(fn combo ->
+        combo != nil
+      end)
+    end)
+    |> Enum.filter(fn combo ->
+      combo != []
+    end)
+
+  end
+
+end
+
+res = Solver.solve(input)
+IO.puts "result: #{inspect res}"