Advent of Code 2021 / D04
Giant Squid - Setup
input =
"inputs/day04.txt"
|> File.read!()testInput = """
7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
22 13 17 11 0
8 2 23 4 24
21 9 14 16 7
6 10 3 18 5
1 12 20 15 19
3 15 0 2 22
9 18 13 17 5
19 8 7 25 23
20 11 10 24 4
14 21 16 12 6
14 21 17 24 4
10 16 15 9 19
18 8 23 26 20
22 11 13 6 5
2 0 12 3 7
"""
defmodule Bingo do
def draw_numbers(input) do
input
|> String.split("\n", trim: true)
|> hd
|> String.split(",")
|> Enum.map(&String.to_integer(&1, 10))
end
def boards(input) do
input
|> String.split("\n", trim: true)
|> then(fn [_hd | tl] -> tl end)
|> Enum.map(&String.split(&1, ~r{\s+}))
|> Enum.map(fn n ->
Enum.filter(n, &(String.length(&1) > 0))
|> Enum.map(fn n -> {String.to_integer(n, 10), 0} end)
end)
|> Enum.chunk_every(5)
end
def mark_board(board, pick) do
board
|> Enum.map(fn row ->
row
|> Enum.map(fn {number, mark} ->
if number == pick, do: {number, 1}, else: {number, mark}
end)
end)
end
defp axis_sum(axis) do
Enum.reduce(axis, 0, fn {_number, mark}, acc -> if mark == 1, do: acc + 1, else: acc end)
end
defp axis_sum(axis, value_check) do
Enum.reduce(axis, 0, fn {number, mark}, acc ->
if mark == value_check, do: acc + number, else: acc
end)
end
def check_winner(board) do
row_won? =
board
|> Enum.map(fn row ->
row
|> Enum.reduce(0, fn {_number, mark}, acc -> if mark == 1, do: acc + 1, else: acc end)
end)
|> Enum.any?(fn x -> x == 5 end)
col_won? =
Enum.any?(0..4, fn col ->
column = Enum.map(0..4, fn i -> board |> Enum.at(i) |> Enum.at(col) end)
axis_sum(column) == 5
end)
# IO.inspect({row_won?, col_won?}, label: "check row and colum win")
Enum.any?([row_won?, col_won?])
end
def sum_unmarked(board) do
Enum.reduce(board, 0, fn row, acc ->
acc + axis_sum(row, 0)
end)
end
endPart 1
For test input.
# mark boards for number
# IO.inspect(testInput |> Bingo.boards |> hd, label: "Boards")
boards = Bingo.boards(testInput)
draw_numbers = Bingo.draw_numbers(testInput)
{board, number} =
Enum.reduce_while(draw_numbers, boards, fn number, boards ->
boards = Enum.map(boards, fn b -> Bingo.mark_board(b, number) end)
if board = Enum.find(boards, &Bingo.check_winner(&1)) do
{:halt, {board, number}}
else
{:cont, boards}
end
end)
IO.inspect({board, number}, label: "winning board & number")
Bingo.sum_unmarked(board) * numberFor realz tho…
boards = Bingo.boards(input)
draw_numbers = Bingo.draw_numbers(input)
{board, number} =
Enum.reduce_while(draw_numbers, boards, fn number, boards ->
boards = Enum.map(boards, fn b -> Bingo.mark_board(b, number) end)
if board = Enum.find(boards, &Bingo.check_winner(&1)) do
{:halt, {board, number}}
else
{:cont, boards}
end
end)
IO.inspect({board, number}, label: "winning board & number")
# should be25023
Bingo.sum_unmarked(board) * numberPart 2
boards = Bingo.boards(input)
draw_numbers = Bingo.draw_numbers(input)
{board, number} =
Enum.reduce_while(draw_numbers, boards, fn number, boards ->
# IO.inspect(number, label: "\nPick")
post_marked_boards = Enum.map(boards, fn b -> Bingo.mark_board(b, number) end)
boards =
post_marked_boards
# |> IO.inspect(label: "predrop")
|> Enum.reject(&Bingo.check_winner(&1))
# IO.inspect(boards, label: "postdrop")
case boards do
[] -> {:halt, {post_marked_boards |> hd, number}}
_ -> {:cont, boards}
end
end)
IO.inspect({board, number}, label: "last winning board & number")
# should be 1924 for test input, 2634 for real input
Bingo.sum_unmarked(board) * numberLearnings
The data structure of the boards is important. I used a tuple, e.g. {number, mark} for each “square”. José’s solution used this data structure:
[
%Board{
grid:
{{false, false, false, false, false}, {false, false, false, false, false},
{false, false, false, false, false}, {false, false, false, false, false},
{false, false, false, false, false}},
numbers: %{
0 => {0, 4},
1 => {4, 0},
2 => {1, 1},
3 => {3, 2},
4 => {1, 3},
5 => {3, 4},
6 => {3, 0},
7 => {2, 4},
8 => {1, 0},
9 => {2, 1},
10 => {3, 1},
11 => {0, 3},
12 => {4, 1},
13 => {0, 1},
14 => {2, 2},
15 => {4, 3},
16 => {2, 3},
17 => {0, 2},
18 => {3, 3},
19 => {4, 4},
20 => {4, 2},
21 => {2, 0},
22 => {0, 0},
23 => {1, 2},
24 => {1, 4}
}
},
%Board{
grid:
{{false, false, false, false, false}, {false, false, false, false, false},
{false, false, false, false, false}, {false, false, false, false, false},
{false, false, false, false, false}},
numbers: %{
0 => {0, 2},
2 => {0, 3},
3 => {0, 0},
4 => {3, 4},
5 => {1, 4},
6 => {4, 4},
7 => {2, 2},
8 => {2, 1},
9 => {1, 0},
10 => {3, 2},
11 => {3, 1},
12 => {4, 3},
13 => {1, 2},
14 => {4, 0},
15 => {0, 1},
16 => {4, 2},
17 => {1, 3},
18 => {1, 1},
19 => {2, 0},
20 => {3, 0},
21 => {4, 1},
22 => {0, 4},
23 => {2, 4},
24 => {3, 3},
25 => {2, 3}
}
},
%Board{
grid:
{{false, false, false, false, false}, {false, false, false, false, false},
{false, false, false, false, false}, {false, false, false, false, false},
{false, false, false, false, false}},
numbers: %{
0 => {4, 1},
2 => {4, 0},
3 => {4, 3},
4 => {0, 4},
5 => {3, 4},
6 => {3, 3},
7 => {4, 4},
8 => {2, 1},
9 => {1, 3},
10 => {1, 0},
11 => {3, 1},
12 => {4, 2},
13 => {3, 2},
14 => {0, 0},
15 => {1, 2},
16 => {1, 1},
17 => {0, 2},
18 => {2, 0},
19 => {1, 4},
20 => {2, 4},
21 => {0, 1},
22 => {3, 0},
23 => {2, 2},
24 => {0, 3},
26 => {2, 3}
}
}
]What’s intersting is how he denormalized the bingo boards and separated the “square’s value” from the position of the numbers on the board. I kept the structure and struggled with finding the right elixir functions to help rangled the data structures.
