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# alkhulaifi's solution

## to Minesweeper in the Elixir Track

Published at Aug 26 2020 · 0 comments
Instructions
Test suite
Solution

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 |
+-----+

## Running tests

Execute the tests with:

\$ mix test

### Pending tests

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

If you're stuck on something, it may help to look at some of the available resources out there where answers might be found.

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### minesweeper_test.exs

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

### test_helper.exs

ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)
defmodule Minesweeper do
@doc """
Annotate empty spots next to mines with the number of mines next to them.
"""
@spec annotate([String.t()]) :: [String.t()]

def annotate(board) do
board
|> Enum.map(&String.codepoints/1)
|> Enum.with_index()
|> Enum.map(fn {line, y} -> line
|> Enum.with_index()
|> Enum.map(fn {pos, x} -> count(board, pos, {y,x}) end)
end)
|> Enum.map(&Enum.join/1)
end

defp get(board,{y,x}) when x >= 0 and y >= 0, do: String.at(Enum.at(board,y,""),x)
defp get(_,_), do: nil

defp count(board, " ", {y,x}) do
(for m <- -1..1, n <- -1..1, do: {m, n})
|> Enum.map(fn {dy, dx} -> get(board,{y+dy,x+dx}) end)
|> Enum.count(fn mine -> mine == "*" end)
|> Integer.to_string()
|> String.replace("0", " ")
end

defp count(_board, mine, _pos), do: mine

end

## Community comments

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### What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?
• Are there new concepts here that you could read more about to improve your understanding?