Day 25HEADmain

1 files changed, 25 insertions, 0 deletions

diff --git a/2015/day25.exs b/2015/day25.exs
new file mode 100644
index 0000000..1aaaa5c
--- /dev/null
+++ b/2015/day25.exs
@@ -0,0 +1,25 @@
+fileContents = File.read!("inputs/day25.txt")
+
+[row, column] =
+  Regex.run(~r/Enter the code at row (\d+), column (\d+)./, fileContents, capture: :all_but_first)
+  |> Enum.map(fn num ->
+    {num, ""} = Integer.parse(num)
+    num
+  end)
+
+codes = Stream.iterate(20_151_125, &rem(&1 * 252_533, 33_554_393))
+
+indices =
+  Stream.iterate({1, 1}, fn
+    {1, col} -> {col + 1, 1}
+    {row, col} -> {row - 1, col + 1}
+  end)
+
+{{^row, ^column}, code} =
+  Stream.zip(indices, codes)
+  |> Enum.find(fn
+    {{^row, ^column}, _} -> true
+    _ -> false
+  end)
+
+IO.puts("Code: #{code}")