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# Day 1

## Load input

```elixir
stream =
  File.stream!("day1.txt")
  |> Stream.map(&String.to_integer(String.trim(&1)))
```

```output
#Stream<[
  enum: %File.Stream{
    line_or_bytes: :line,
    modes: [:raw, :read_ahead, :binary],
    path: "day1.txt",
    raw: true
  },
  funs: [#Function<47.58486609/1 in Stream.map/2>]
]>
```

## Task 1

Compute count of consecutive increases

```elixir
stream
|> Stream.chunk_every(2, 1, :discard)
|> Enum.count(fn [a, b] -> a < b end)
```

```output
1688
```

## Task 2

Compute count of consecutive increases of sums of trigrams.

However we can notice, that if we have list like:

$$
[a, b, c, d]
$$

Then when we want to compare consecutive trigrams then we compare:

$$
a + b + c < b + c + d \\
a < d
$$

So we can traverse each 4 elements and then just compare first and last one
instead of summing and then traversing it again.

```elixir
stream
|> Stream.chunk_every(4, 1, :discard)
|> Enum.count(fn [a, _, _, b] -> a < b end)
```

```output
1728
```