# Minesweeper

Welcome to Minesweeper on Exercism's Rust Track.
If you need help running the tests or submitting your code, check out `HELP.md`.

## Instructions

Add the mine counts to a completed 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 given empty square and replaces that square with the count.

The board is a rectangle composed of blank space (' ') characters.
A mine is represented by an asterisk (`*`) character.

If a given space has no adjacent mines at all, leave that square blank.

## Examples

For example you may receive a 5 x 4 board like this (empty spaces are represented here with the '·' character for display on screen):

```text
·*·*·
··*··
··*··
·····
```

And your code will transform it into this:

```text
1*3*1
13*31
·2*2·
·111·
```

## Performance Hint

All the inputs and outputs are in ASCII.
Rust `String`s and `&str` are utf8, so while one might expect `"Hello".chars()` to be simple, it actually has to check each char to see if it's 1, 2, 3 or 4 `u8`s long.
If we know a `&str` is ASCII then we can call `.as_bytes()` and refer to the underlying data as a `&[u8]` (byte slice).
Iterating over a slice of ASCII bytes is much quicker as there are no codepoints involved - every ASCII byte is one `u8` long.

Can you complete the challenge without cloning the input?

## Source

### Created by

- @EduardoBautista

### Contributed to by

- @ashleygwilliams
- @coriolinus
- @cwhakes
- @EduardoBautista
- @efx
- @ErikSchierboom
- @ffflorian
- @IanWhitney
- @kytrinyx
- @lutostag
- @mkantor
- @nfiles
- @petertseng
- @rofrol
- @stringparser
- @workingjubilee
- @xakon
- @ZapAnton