Exercise: Mazy Mice

config.json

@@ -577,6 +577,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 4
+      },
+      {
+        "slug": "mazy-mice",
+        "name": "Mazy Mice",
+        "uuid": "a1e388fe-9c4b-4a02-b922-423dce834cb0",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
       }
     ]
   },

exercises/practice/mazy-mice/.docs/hints.md

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+# placeholder
+
+## General
+
+- The `rand` [numeric function][rand-func] can generate random numbers.
+- The `srand` [numeric function][srand-func] will be helpful to set the seed for `rand`.
+
+## Maze generation
+
+You can use any algorithm to generate a perfect maze. The [recursive backtracker][recursive-backtracker] is a good choice.
+
+## Box drawing characters
+
+| Character | Name                                  | Unicode |
+|:---------:|:--------------------------------------|:--------|
+|     ┌     | box drawings light down and right     |  U+250C |
+|     ─     | box drawings light horizontal         |  U+2500 |
+|     ┬     | box drawings light down and horizontal|  U+252C |
+|     ┐     | box drawings light down and left      |  U+2510 |
+|     │     | box drawings light vertical           |  U+2502 |
+|     └     | box drawings light up and right       |  U+2514 |
+|     ┴     | box drawings light up and horizontal  |  U+2534 |
+|     ┘     | box drawings light up and left        |  U+2518 |
+|     ├     | box drawings light vertical and right |  U+2520 |
+|     ⇨     | rightwards white arrow                |  U+21E8 |
+
+
+[rand-func]: https://www.gnu.org/software/gawk/manual/html_node/Numeric-Functions.html#index-rand_0028_0029-function
+[srand-func]: https://www.gnu.org/software/gawk/manual/html_node/Numeric-Functions.html#index-srand_0028_0029-function
+[recursive-backtracker]: https://en.wikipedia.org/wiki/Maze_generation_algorithm

exercises/practice/mazy-mice/.docs/instructions.md

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+## Instructions
+
+Your task is to generate the perfect mazes for Mickey and Minerva — those with only one solution and no isolated sections. 
+Here's what you need to know:
+
+- The maze has a rectangular shape with an opening at the start and end.
+- The maze has rooms and passages, which intersect at right angles.
+- The program should accept two parameters: rows and columns. The maze should be between 5 and 100 cells in size.
+- A maze which is `x` columns wide and `y` rows high should be `2x + 1` characters wide and `2y + 1` characters high.
+- If no seed is provided, generate a random maze. If the same seed is provided multiple times, the resulting maze should be the same each time.
+- Use [box-drawing][Box-drawing] characters to draw walls, and an arrow symbol (⇨) for the entrance on the left and exit on the right.
+
+It's time to create some perfect mazes for these adventurous mice!
+
+### Examples
+
+1. The small square maze 5x5 cells (or 11x11 characters)
+```text
+	┌───────┬─┐
+	│       │ │
+	│ ┌─┬── │ │
+	│ │ │   │ ⇨
+	│ │ │ ──┤ │
+	⇨ │ │   │ │
+	┌─┤ └── │ │
+	│ │     │ │
+	│ │ ────┘ │
+	│         │
+	└─────────┘
+```
+2. The rectangular maze 6x18 cells
+```text
+	┌───────────┬─────────┬───────────┬─┐
+	│           │         │           │ │
+	│ ┌───────┐ │ ┌─┐ ──┐ └───┐ ┌───┐ │ │
+	│ │       │ │ │ │   │     │ │   │   ⇨
+	│ └─┐ ┌─┐ │ │ │ ├── ├───┐ │ │ ──┼── │
+	│   │ │ │   │   │   │   │ │ │   │   │
+	└── │ │ ├───┴───┤ ┌─┘ ┌─┘ │ ├── │ ──┤
+	⇨   │   │       │ │   │   │ │   │   │
+	┌─┬─┴─┐ └─┐ ┌─┐ │ └─┐ │ ┌─┘ │ ──┴─┐ │
+	│ │   │   │ │ │ │   │   │   │     │ │
+	│ │ │ └── │ │ │ └── │ ──┘ ┌─┘ ──┐ │ │
+	│   │       │       │     │     │   │
+	└───┴───────┴───────┴─────┴─────┴───┘
+```
+
+[Box-drawing]: https://en.wikipedia.org/wiki/Box-drawing_character

exercises/practice/mazy-mice/.docs/introduction.md

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+# Introduction
+
+Meet Mickey and Minerva, two clever mice who love to navigate their way through a maze to find cheese. They enjoy a good challenge, but with only their tiny mouse brains, they prefer if there is only one correct path to the cheese.

exercises/practice/mazy-mice/.meta/config.json

@@ -0,0 +1,22 @@
+{
+  "authors": [
+    "rabestro"
+  ],
+  "files": {
+    "solution": [
+      "mazy-mice.awk"
+    ],
+    "test": [
+      "test-mazy-mice.bats"
+    ],
+    "example": [
+      ".meta/example.awk"
+    ],
+    "editor": [
+      "test-maze.awk"
+    ]
+  },
+  "blurb": "Meet Mickey and Minerva, two clever mice who love to navigate their way through a maze to find cheese. They enjoy a good challenge, but with only their tiny mouse brains, they prefer if there is only one correct path to the cheese.",
+  "source": "Inspired by the 'Maze Generator' created by Jan Boström at Alance AB.",
+  "source_url": "https://mazegenerator.net/"
+}

exercises/practice/mazy-mice/.meta/example.awk

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+BEGIN {
+    OFS = ""
+    Rows = Rows ? Rows : 8
+    Cols = Cols ? Cols : 16
+    Seed ? srand(Seed) : srand()
+
+    Width = 2 * Cols + 1
+    Height = 2 * Rows + 1
+
+    create_grid()
+    generate_maze(1, 1)
+    arrange_doors()
+    print_maze()
+}
+
+function create_grid(    row, col) {
+    for (row = 0; row < Height; row++)
+        for (col = 0; col < Width; col++)
+            Grid[row, col] = 1
+}
+function print_maze(   row, col) {
+    for (row = 0; row < Height; row++) {
+        for (col = 0; col < Width; col++)
+            $(col + 1) = symbol(row, col)
+        print
+    }
+}
+
+# Recursive backtracking algorithm
+function generate_maze(row, col,   directions,randDir,dx,dy,newRow,newCol) {
+    Grid[row, col] = 0
+
+    directions = "NESW"
+    while (length(directions) > 0) {
+        randDir = substr(directions, int(rand() * length(directions)) + 1, 1)
+        sub(randDir, "", directions)
+
+        dx = dy = 0
+        if (randDir == "N") dy = -2
+        if (randDir == "E") dx = 2
+        if (randDir == "S") dy = 2
+        if (randDir == "W") dx = -2
+        newRow = row + dy
+        newCol = col + dx
+
+        if (newRow > 0 && newRow < Height && newCol > 0 && newCol < Width && Grid[newRow, newCol]) {
+            Grid[row + dy / 2, col + dx / 2] = 0
+            generate_maze(newRow, newCol)
+        }
+    }
+}
+function arrange_doors() {
+    MazeEntrance = 1 + 2 * int(rand() * Rows)
+    MazeExit = 1 + 2 * int(rand() * Rows)
+}
+function symbol(row, col,   n,e,s,w) {
+    if (!Grid[row, col]) return " "
+    if (is_door(row, col)) return "⇨"
+    n = row ? Grid[row - 1, col] : 0
+    e = col < Width - 1 ? Grid[row, col + 1] : 0
+    s = row < Height - 1 ? Grid[row + 1, col] : 0
+    w = col ? Grid[row, col - 1] : 0
+    return substr(" │─└││┌├─┘─┴┐┤┬┼", 1 + n + 2 * e + 4 * s + 8 * w, 1)
+}
+
+function is_door(row, col) {return row == MazeEntrance && col == 0 || row == MazeExit && col == Width - 1}