Add the numbers to a minesweeper board.
Minesweeper is a popular game where the user has to find the mines using numeric hints that indicate how many mines are directly adjacent (horizontally, vertically, diagonally) to a square.
In this exercise you have to create some code that counts the number of
mines adjacent to a square and transforms boards like this (where *
indicates a mine):
+-----+
| * * |
| * |
| * |
| |
+-----+
into this:
+-----+
|1*3*1|
|13*31|
| 2*2 |
| 111 |
+-----+
Execute the tests with:
$ elixir minesweeper_test.exs
In the test suites, all but the first test have been skipped.
Once you get a test passing, you can unskip the next one by
commenting out the relevant @tag :pending
with a #
symbol.
For example:
# @tag :pending
test "shouting" do
assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end
Or, you can enable all the tests by commenting out the
ExUnit.configure
line in the test suite.
# ExUnit.configure exclude: :pending, trace: true
For more detailed information about the Elixir track, please see the help page.
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
if !System.get_env("EXERCISM_TEST_EXAMPLES") do
Code.load_file("minesweeper.exs", __DIR__)
end
ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)
defmodule MinesweeperTest do
use ExUnit.Case
defp clean(b), do: Enum.map(b, &String.replace(&1, ~r/[^*]/, " "))
# @tag :pending
test "zero size board" do
b = []
assert Minesweeper.annotate(clean(b)) == b
end
@tag :pending
test "empty board" do
b = [" ", " ", " "]
assert Minesweeper.annotate(clean(b)) == b
end
@tag :pending
test "board full of mines" do
b = ["***", "***", "***"]
assert Minesweeper.annotate(clean(b)) == b
end
@tag :pending
test "surrounded" do
b = ["***", "*8*", "***"]
assert Minesweeper.annotate(clean(b)) == b
end
@tag :pending
test "horizontal line" do
b = ["1*2*1"]
assert Minesweeper.annotate(clean(b)) == b
end
@tag :pending
test "vertical line" do
b = ["1", "*", "2", "*", "1"]
assert Minesweeper.annotate(clean(b)) == b
end
@tag :pending
test "cross" do
b = [" 2*2 ", "25*52", "*****", "25*52", " 2*2 "]
assert Minesweeper.annotate(clean(b)) == b
end
end
defmodule Minesweeper do
@doc """
Annotate empty spots next to mines with the number of mines next to them.
"""
@spec annotate([String.t]) :: [String.t]
@neighbors [{-1, -1}, {-1, 0}, {-1, 1}, {0, 1}, {1, 1}, {1, 0}, {1, -1}, {0, -1}]
def annotate(board) do
print(board, count(board))
end
defp count(board) do
board
|> Enum.with_index(0)
|> Enum.reduce(%{}, fn({row, row_index}, acc_rows) ->
row
|> String.graphemes
|> Enum.with_index(0)
|> Enum.reduce(acc_rows, fn({field, column_index}, acc_fields) ->
case field do
" " -> acc_fields
"*" ->
acc_fields
|> Map.put({column_index, row_index}, "*")
|> count_up_neighbors({column_index, row_index})
end
end)
end)
end
defp count_up_neighbors(board, {column_index, row_index}) do
@neighbors
|> Enum.reduce(board, fn({column_delta, row_delta}, acc) ->
acc
|> Map.update({column_index + column_delta, row_index + row_delta}, 1, &(count_up(&1)))
end)
end
defp count_up(field) do
case field do
"*" -> "*"
x -> x + 1
end
end
defp print(board, board_with_counts) do
board
|> Enum.with_index(0)
|> Enum.map(fn({row, row_index}) ->
row
|> String.graphemes
|> Enum.with_index(0)
|> Enum.reduce("", fn({field, column_index}, acc) ->
acc <> case Map.get(board_with_counts, {column_index, row_index}) do
nil -> " "
x -> "#{x}"
end
end)
end)
end
end
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