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## to Minesweeper in the OCaml Track

Published at Jul 23 2020 · 1 comment
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 |
+-----+
``````

## Getting Started

1. For library documentation, follow Useful OCaml resources.

## Running Tests

A `Makefile` is provided with a default target to compile your solution and run the tests. At the command line, type:

``````make
``````

## Submitting Incomplete Solutions

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

## Feedback, Issues, Pull Requests

The exercism/ocaml repository on GitHub is the home for all of the Ocaml exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue or submit a PR. We welcome new contributors!

### test.ml

``````(* minesweeper - 1.1.0 *)
open Base
open OUnit2
open Minesweeper

let format_board strings =
let width = match strings with
| [] -> 0
| (s::_) -> String.length s in
let border_line = "+" ^ String.make width '-' ^ "+\n" in
let line s = "|" ^ s ^ "|\n" in
"\n" ^ border_line ^ String.concat (List.map strings ~f:line) ^ border_line

(* Assert Equals *)
let ae exp got =
assert_equal exp got ~printer:format_board

let tests = [
"no rows" >:: (fun _ ->
let b = [] in
let expected = [] in
ae expected (annotate b)
);
"no columns" >:: (fun _ ->
let b = [""] in
let expected = [""] in
ae expected (annotate b)
);
"no mines" >:: (fun _ ->
let b = [
"   ";
"   ";
"   ";
] in
let expected = [
"   ";
"   ";
"   ";
] in
ae expected (annotate b)
);
"minefield with only mines" >:: (fun _ ->
let b = [
"***";
"***";
"***";
] in
let expected = [
"***";
"***";
"***";
] in
ae expected (annotate b)
);
"mine surrounded by spaces" >:: (fun _ ->
let b = [
"   ";
" * ";
"   ";
] in
let expected = [
"111";
"1*1";
"111";
] in
ae expected (annotate b)
);
"space surrounded by mines" >:: (fun _ ->
let b = [
"***";
"* *";
"***";
] in
let expected = [
"***";
"*8*";
"***";
] in
ae expected (annotate b)
);
"horizontal line" >:: (fun _ ->
let b = [" * * "] in
let expected = ["1*2*1"] in
ae expected (annotate b)
);
"horizontal line, mines at edges" >:: (fun _ ->
let b = ["*   *"] in
let expected = ["*1 1*"] in
ae expected (annotate b)
);
"vertical line" >:: (fun _ ->
let b = [
" ";
"*";
" ";
"*";
" ";
] in
let expected = [
"1";
"*";
"2";
"*";
"1";
] in
ae expected (annotate b)
);
"vertical line, mines at edges" >:: (fun _ ->
let b = [
"*";
" ";
" ";
" ";
"*";
] in
let expected = [
"*";
"1";
" ";
"1";
"*";
] in
ae expected (annotate b)
);
"cross" >:: (fun _ ->
let b = [
"  *  ";
"  *  ";
"*****";
"  *  ";
"  *  ";
] in
let expected = [
" 2*2 ";
"25*52";
"*****";
"25*52";
" 2*2 ";
] in
ae expected (annotate b)
);
"large minefield" >:: (fun _ ->
let b = [
" *  * ";
"  *   ";
"    * ";
"   * *";
" *  * ";
"      ";
] in
let expected = [
"1*22*1";
"12*322";
" 123*2";
"112*4*";
"1*22*2";
"111111";
] in
ae expected (annotate b)
);
]

let () =
run_test_tt_main ("minesweeper tests" >::: tests)``````
``````let getitem (row, col) board =
try       Some Bytes.(get board.(row) col)
with _ -> None

let cells = [ (-1,-1); (-1, 0); (-1, 1)
; (0, -1); (*0, 0*) (0,  1)
; (1, -1); (1,  0); (1,  1) ]

let bump = function
| '1'..'7' as c -> Char.(chr (code c + 1))
| ' ' -> '1'
| c -> c

let annotate ls =
let board = ls |> Array.of_list
|> Array.map Bytes.of_string
in
let flag rmine cmine =
let surround (r, c) =
match getitem (r+rmine, c+cmine) board with
| Some a ->
board.(r+rmine).[c+cmine] <- bump a
| None -> ()
in
List.iter surround cells
in
board |> Array.iteri
(fun r -> Bytes.iteri
(fun c chr -> if chr = '*' then flag r c));

board |> Array.map Bytes.to_string
|> Array.to_list`````` Solution Author
commented 99 days ago

Why were the tests and interface specified with immutable structures (List, String) when the problem seems to be of a mutable nature?

I found myself solving more naturally with Array and Bytes

### What can you learn from this solution?

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