{"title":"Exercise: Realization","description":null,"content":"Try implementing the below code exercises to reinforce your understanding. Your goal is to implement the classes below so that they produce the expected output.\n\n---\n\n# Exercise 1: Shape Drawing System\n\n\n**Problem:** Build a drawing system where different shapes implement a common `Drawable` interface. A `Canvas` class renders all shapes through the interface without knowing the concrete types.\n\n**Requirements:**\n\n- `Drawable` interface with `draw()` and `getArea()` methods.\n- `Circle` with a radius, `Rectangle` with width and height, `Triangle` with base and height. All three implement `Drawable`.\n- `Canvas` with a `drawAll(shapes)` method that iterates over a list of `Drawable` objects, calls `draw()` on each, and prints the area.\n\n```java\nimport java.util.List;\n\ninterface Drawable {\n void draw();\n double getArea();\n}\n\nclass Circle implements Drawable {\n private double radius;\n\n public Circle(double radius) {\n this.radius = radius;\n }\n\n public void draw() {\n // TODO: print \"Drawing circle with radius X\"\n }\n\n public double getArea() {\n // TODO: return π * r²\n return 0;\n }\n}\n\nclass Rectangle implements Drawable {\n private double width;\n private double height;\n\n public Rectangle(double width, double height) {\n this.width = width;\n this.height = height;\n }\n\n public void draw() {\n // TODO: print \"Drawing rectangle WxH\"\n }\n\n public double getArea() {\n // TODO: return width * height\n return 0;\n }\n}\n\nclass Triangle implements Drawable {\n private double base;\n private double height;\n\n public Triangle(double base, double height) {\n this.base = base;\n this.height = height;\n }\n\n public void draw() {\n // TODO: print \"Drawing triangle with base B and height H\"\n }\n\n public double getArea() {\n // TODO: return 0.5 * base * height\n return 0;\n }\n}\n\nclass Canvas {\n public void drawAll(List shapes) {\n // TODO: For each shape, call draw() and print its area\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n Canvas canvas = new Canvas();\n\n List shapes = List.of(\n new Circle(5.0),\n new Rectangle(4.0, 6.0),\n new Triangle(3.0, 8.0)\n );\n\n canvas.drawAll(shapes);\n }\n}\n```\n\n```python\nfrom abc import ABC, abstractmethod\nimport math\n\nclass Drawable(ABC):\n @abstractmethod\n def draw(self):\n pass\n\n @abstractmethod\n def get_area(self):\n pass\n\nclass Circle(Drawable):\n def __init__(self, radius):\n self.radius = radius\n\n def draw(self):\n pass # TODO: print \"Drawing circle with radius X\"\n\n def get_area(self):\n return 0 # TODO: return π * r²\n\nclass Rectangle(Drawable):\n def __init__(self, width, height):\n self.width = width\n self.height = height\n\n def draw(self):\n pass # TODO: print \"Drawing rectangle WxH\"\n\n def get_area(self):\n return 0 # TODO: return width * height\n\nclass Triangle(Drawable):\n def __init__(self, base, height):\n self.base = base\n self.height = height\n\n def draw(self):\n pass # TODO: print \"Drawing triangle with base B and height H\"\n\n def get_area(self):\n return 0 # TODO: return 0.5 * base * height\n\nclass Canvas:\n def draw_all(self, shapes):\n # TODO: For each shape, call draw() and print its area\n pass\n\nif __name__ == \"__main__\":\n canvas = Canvas()\n\n shapes = [\n Circle(5.0),\n Rectangle(4.0, 6.0),\n Triangle(3.0, 8.0),\n ]\n\n canvas.draw_all(shapes)\n```\n\n```cpp\n#include \n#include \n#include \n#include \nusing namespace std;\n\nclass Drawable {\npublic:\n virtual void draw() = 0;\n virtual double getArea() = 0;\n virtual ~Drawable() = default;\n};\n\nclass Circle : public Drawable {\nprivate:\n double radius;\npublic:\n Circle(double radius) : radius(radius) {}\n\n void draw() override {\n // TODO: print \"Drawing circle with radius X\"\n }\n\n double getArea() override {\n // TODO: return π * r²\n return 0;\n }\n};\n\nclass Rectangle : public Drawable {\nprivate:\n double width, height;\npublic:\n Rectangle(double width, double height) : width(width), height(height) {}\n\n void draw() override {\n // TODO: print \"Drawing rectangle WxH\"\n }\n\n double getArea() override {\n // TODO: return width * height\n return 0;\n }\n};\n\nclass Triangle : public Drawable {\nprivate:\n double base, height;\npublic:\n Triangle(double base, double height) : base(base), height(height) {}\n\n void draw() override {\n // TODO: print \"Drawing triangle with base B and height H\"\n }\n\n double getArea() override {\n // TODO: return 0.5 * base * height\n return 0;\n }\n};\n\nclass Canvas {\npublic:\n void drawAll(vector>& shapes) {\n // TODO: For each shape, call draw() and print its area\n }\n};\n\nint main() {\n Canvas canvas;\n\n vector> shapes;\n shapes.push_back(make_unique(5.0));\n shapes.push_back(make_unique(4.0, 6.0));\n shapes.push_back(make_unique(3.0, 8.0));\n\n canvas.drawAll(shapes);\n\n return 0;\n}\n```\n\n```go\npackage main\n\ntype Drawable interface {\n\tDraw()\n\tGetArea() float64\n}\n\ntype Circle struct {\n\tradius float64\n}\n\nfunc NewCircle(radius float64) *Circle {\n\treturn &Circle{radius: radius}\n}\n\nfunc (c *Circle) Draw() {\n\t// TODO: print \"Drawing circle with radius X\"\n}\n\nfunc (c *Circle) GetArea() float64 {\n\t// TODO: return π * r²\n\treturn 0\n}\n\ntype Rectangle struct {\n\twidth float64\n\theight float64\n}\n\nfunc NewRectangle(width float64, height float64) *Rectangle {\n\treturn &Rectangle{width: width, height: height}\n}\n\nfunc (r *Rectangle) Draw() {\n\t// TODO: print \"Drawing rectangle WxH\"\n}\n\nfunc (r *Rectangle) GetArea() float64 {\n\t// TODO: return width * height\n\treturn 0\n}\n\ntype Triangle struct {\n\tbase float64\n\theight float64\n}\n\nfunc NewTriangle(base float64, height float64) *Triangle {\n\treturn &Triangle{base: base, height: height}\n}\n\nfunc (t *Triangle) Draw() {\n\t// TODO: print \"Drawing triangle with base B and height H\"\n}\n\nfunc (t *Triangle) GetArea() float64 {\n\t// TODO: return 0.5 * base * height\n\treturn 0\n}\n\ntype Canvas struct {\n}\n\nfunc NewCanvas() *Canvas {\n\treturn &Canvas{}\n}\n\nfunc (c *Canvas) DrawAll(shapes []Drawable) {\n\t// TODO: For each shape, call draw() and print its area\n}\n\nfunc main() {\n\tcanvas := NewCanvas()\n\n\tshapes := []Drawable{\n\t\tNewCircle(5.0),\n\t\tNewRectangle(4.0, 6.0),\n\t\tNewTriangle(3.0, 8.0),\n\t}\n\n\tcanvas.DrawAll(shapes)\n}\n```\n\n```csharp\nusing System;\nusing System.Collections.Generic;\n\ninterface IDrawable\n{\n void Draw();\n double GetArea();\n}\n\nclass Circle : IDrawable\n{\n private double radius;\n\n public Circle(double radius) { this.radius = radius; }\n\n public void Draw()\n {\n // TODO: print \"Drawing circle with radius X\"\n }\n\n public double GetArea()\n {\n // TODO: return π * r²\n return 0;\n }\n}\n\nclass Rectangle : IDrawable\n{\n private double width, height;\n\n public Rectangle(double width, double height)\n {\n this.width = width;\n this.height = height;\n }\n\n public void Draw()\n {\n // TODO: print \"Drawing rectangle WxH\"\n }\n\n public double GetArea()\n {\n // TODO: return width * height\n return 0;\n }\n}\n\nclass Triangle : IDrawable\n{\n private double baseLen, height;\n\n public Triangle(double baseLen, double height)\n {\n this.baseLen = baseLen;\n this.height = height;\n }\n\n public void Draw()\n {\n // TODO: print \"Drawing triangle with base B and height H\"\n }\n\n public double GetArea()\n {\n // TODO: return 0.5 * base * height\n return 0;\n }\n}\n\nclass Canvas\n{\n public void DrawAll(List shapes)\n {\n // TODO: For each shape, call Draw() and print its area\n }\n}\n\nclass Program\n{\n static void Main()\n {\n var canvas = new Canvas();\n\n var shapes = new List\n {\n new Circle(5.0),\n new Rectangle(4.0, 6.0),\n new Triangle(3.0, 8.0)\n };\n\n canvas.DrawAll(shapes);\n }\n}\n```\n\n```typescript\ninterface Drawable {\n draw(): void;\n getArea(): number;\n}\n\nclass Circle implements Drawable {\n private radius: number;\n\n constructor(radius: number) { this.radius = radius; }\n\n draw(): void {\n // TODO: print \"Drawing circle with radius X\"\n }\n\n getArea(): number {\n // TODO: return π * r²\n return 0;\n }\n}\n\nclass Rectangle implements Drawable {\n private width: number;\n private height: number;\n\n constructor(width: number, height: number) {\n this.width = width;\n this.height = height;\n }\n\n draw(): void {\n // TODO: print \"Drawing rectangle WxH\"\n }\n\n getArea(): number {\n // TODO: return width * height\n return 0;\n }\n}\n\nclass Triangle implements Drawable {\n private base: number;\n private height: number;\n\n constructor(base: number, height: number) {\n this.base = base;\n this.height = height;\n }\n\n draw(): void {\n // TODO: print \"Drawing triangle with base B and height H\"\n }\n\n getArea(): number {\n // TODO: return 0.5 * base * height\n return 0;\n }\n}\n\nclass Canvas {\n drawAll(shapes: Drawable[]): void {\n // TODO: For each shape, call draw() and print its area\n }\n}\n\nconst canvas = new Canvas();\n\nconst shapes: Drawable[] = [\n new Circle(5.0),\n new Rectangle(4.0, 6.0),\n new Triangle(3.0, 8.0),\n];\n\ncanvas.drawAll(shapes);\n```\n\n#### Solutions\n\n```java\nimport java.util.List;\n\ninterface Drawable {\n void draw();\n double getArea();\n}\n\nclass Circle implements Drawable {\n private double radius;\n\n public Circle(double radius) {\n this.radius = radius;\n }\n\n public void draw() {\n System.out.println(\"Drawing circle with radius \" + radius);\n }\n\n public double getArea() {\n return Math.PI * radius * radius;\n }\n}\n\nclass Rectangle implements Drawable {\n private double width;\n private double height;\n\n public Rectangle(double width, double height) {\n this.width = width;\n this.height = height;\n }\n\n public void draw() {\n System.out.println(\"Drawing rectangle \" + width + \"x\" + height);\n }\n\n public double getArea() {\n return width * height;\n }\n}\n\nclass Triangle implements Drawable {\n private double base;\n private double height;\n\n public Triangle(double base, double height) {\n this.base = base;\n this.height = height;\n }\n\n public void draw() {\n System.out.println(\"Drawing triangle with base \" + base + \" and height \" + height);\n }\n\n public double getArea() {\n return 0.5 * base * height;\n }\n}\n\nclass Canvas {\n public void drawAll(List shapes) {\n for (Drawable shape : shapes) {\n shape.draw();\n System.out.printf(\" Area: %.2f%n%n\", shape.getArea());\n }\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n Canvas canvas = new Canvas();\n\n List shapes = List.of(\n new Circle(5.0),\n new Rectangle(4.0, 6.0),\n new Triangle(3.0, 8.0)\n );\n\n canvas.drawAll(shapes);\n }\n}\n```\n\n```python\nfrom abc import ABC, abstractmethod\nimport math\n\nclass Drawable(ABC):\n @abstractmethod\n def draw(self):\n pass\n\n @abstractmethod\n def get_area(self):\n pass\n\nclass Circle(Drawable):\n def __init__(self, radius):\n self.radius = radius\n\n def draw(self):\n print(f\"Drawing circle with radius {self.radius}\")\n\n def get_area(self):\n return math.pi * self.radius * self.radius\n\nclass Rectangle(Drawable):\n def __init__(self, width, height):\n self.width = width\n self.height = height\n\n def draw(self):\n print(f\"Drawing rectangle {self.width}x{self.height}\")\n\n def get_area(self):\n return self.width * self.height\n\nclass Triangle(Drawable):\n def __init__(self, base, height):\n self.base = base\n self.height = height\n\n def draw(self):\n print(f\"Drawing triangle with base {self.base} and height {self.height}\")\n\n def get_area(self):\n return 0.5 * self.base * self.height\n\nclass Canvas:\n def draw_all(self, shapes):\n for shape in shapes:\n shape.draw()\n print(f\" Area: {shape.get_area():.2f}\\n\")\n\nif __name__ == \"__main__\":\n canvas = Canvas()\n\n shapes = [\n Circle(5.0),\n Rectangle(4.0, 6.0),\n Triangle(3.0, 8.0),\n ]\n\n canvas.draw_all(shapes)\n```\n\n```cpp\n#include \n#include \n#include \n#include \nusing namespace std;\n\nclass Drawable {\npublic:\n virtual void draw() = 0;\n virtual double getArea() = 0;\n virtual ~Drawable() = default;\n};\n\nclass Circle : public Drawable {\nprivate:\n double radius;\npublic:\n Circle(double radius) : radius(radius) {}\n\n void draw() override {\n printf(\"Drawing circle with radius %.1f\\n\", radius);\n }\n\n double getArea() override {\n return M_PI * radius * radius;\n }\n};\n\nclass Rectangle : public Drawable {\nprivate:\n double width, height;\npublic:\n Rectangle(double width, double height) : width(width), height(height) {}\n\n void draw() override {\n printf(\"Drawing rectangle %.1fx%.1f\\n\", width, height);\n }\n\n double getArea() override {\n return width * height;\n }\n};\n\nclass Triangle : public Drawable {\nprivate:\n double base, height;\npublic:\n Triangle(double base, double height) : base(base), height(height) {}\n\n void draw() override {\n printf(\"Drawing triangle with base %.1f and height %.1f\\n\", base, height);\n }\n\n double getArea() override {\n return 0.5 * base * height;\n }\n};\n\nclass Canvas {\npublic:\n void drawAll(vector>& shapes) {\n for (auto& shape : shapes) {\n shape->draw();\n printf(\" Area: %.2f\\n\\n\", shape->getArea());\n }\n }\n};\n\nint main() {\n Canvas canvas;\n\n vector> shapes;\n shapes.push_back(make_unique(5.0));\n shapes.push_back(make_unique(4.0, 6.0));\n shapes.push_back(make_unique(3.0, 8.0));\n\n canvas.drawAll(shapes);\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport (\n\t\"fmt\"\n\t\"math\"\n)\n\ntype Drawable interface {\n\tDraw()\n\tGetArea() float64\n}\n\ntype Circle struct {\n\tradius float64\n}\n\nfunc NewCircle(radius float64) *Circle {\n\treturn &Circle{radius: radius}\n}\n\nfunc (c *Circle) Draw() {\n\tfmt.Printf(\"Drawing circle with radius %.1f\\n\", c.radius)\n}\n\nfunc (c *Circle) GetArea() float64 {\n\treturn math.Pi * c.radius * c.radius\n}\n\ntype Rectangle struct {\n\twidth float64\n\theight float64\n}\n\nfunc NewRectangle(width, height float64) *Rectangle {\n\treturn &Rectangle{width: width, height: height}\n}\n\nfunc (r *Rectangle) Draw() {\n\tfmt.Printf(\"Drawing rectangle %.1fx%.1f\\n\", r.width, r.height)\n}\n\nfunc (r *Rectangle) GetArea() float64 {\n\treturn r.width * r.height\n}\n\ntype Triangle struct {\n\tbase float64\n\theight float64\n}\n\nfunc NewTriangle(base, height float64) *Triangle {\n\treturn &Triangle{base: base, height: height}\n}\n\nfunc (t *Triangle) Draw() {\n\tfmt.Printf(\"Drawing triangle with base %.1f and height %.1f\\n\", t.base, t.height)\n}\n\nfunc (t *Triangle) GetArea() float64 {\n\treturn 0.5 * t.base * t.height\n}\n\ntype Canvas struct{}\n\nfunc (c *Canvas) DrawAll(shapes []Drawable) {\n\tfor _, shape := range shapes {\n\t\tshape.Draw()\n\t\tfmt.Printf(\" Area: %.2f\\n\\n\", shape.GetArea())\n\t}\n}\n\nfunc main() {\n\tcanvas := &Canvas{}\n\n\tshapes := []Drawable{\n\t\tNewCircle(5.0),\n\t\tNewRectangle(4.0, 6.0),\n\t\tNewTriangle(3.0, 8.0),\n\t}\n\n\tcanvas.DrawAll(shapes)\n}\n```\n\n```csharp\nusing System;\nusing System.Collections.Generic;\n\ninterface IDrawable\n{\n void Draw();\n double GetArea();\n}\n\nclass Circle : IDrawable\n{\n private double radius;\n\n public Circle(double radius) { this.radius = radius; }\n\n public void Draw()\n {\n Console.WriteLine($\"Drawing circle with radius {radius:F1}\");\n }\n\n public double GetArea()\n {\n return Math.PI * radius * radius;\n }\n}\n\nclass Rectangle : IDrawable\n{\n private double width, height;\n\n public Rectangle(double width, double height)\n {\n this.width = width;\n this.height = height;\n }\n\n public void Draw()\n {\n Console.WriteLine($\"Drawing rectangle {width:F1}x{height:F1}\");\n }\n\n public double GetArea()\n {\n return width * height;\n }\n}\n\nclass Triangle : IDrawable\n{\n private double baseLen, height;\n\n public Triangle(double baseLen, double height)\n {\n this.baseLen = baseLen;\n this.height = height;\n }\n\n public void Draw()\n {\n Console.WriteLine($\"Drawing triangle with base {baseLen:F1} and height {height:F1}\");\n }\n\n public double GetArea()\n {\n return 0.5 * baseLen * height;\n }\n}\n\nclass Canvas\n{\n public void DrawAll(List shapes)\n {\n foreach (var shape in shapes)\n {\n shape.Draw();\n Console.WriteLine($\" Area: {shape.GetArea():F2}\\n\");\n }\n }\n}\n\nclass Program\n{\n static void Main()\n {\n var canvas = new Canvas();\n\n var shapes = new List\n {\n new Circle(5.0),\n new Rectangle(4.0, 6.0),\n new Triangle(3.0, 8.0)\n };\n\n canvas.DrawAll(shapes);\n }\n}\n```\n\n```typescript\ninterface Drawable {\n draw(): void;\n getArea(): number;\n}\n\nclass Circle implements Drawable {\n private radius: number;\n\n constructor(radius: number) { this.radius = radius; }\n\n draw(): void {\n console.log(`Drawing circle with radius ${this.radius.toFixed(1)}`);\n }\n\n getArea(): number {\n return Math.PI * this.radius * this.radius;\n }\n}\n\nclass Rectangle implements Drawable {\n private width: number;\n private height: number;\n\n constructor(width: number, height: number) {\n this.width = width;\n this.height = height;\n }\n\n draw(): void {\n console.log(`Drawing rectangle ${this.width.toFixed(1)}x${this.height.toFixed(1)}`);\n }\n\n getArea(): number {\n return this.width * this.height;\n }\n}\n\nclass Triangle implements Drawable {\n private base: number;\n private height: number;\n\n constructor(base: number, height: number) {\n this.base = base;\n this.height = height;\n }\n\n draw(): void {\n console.log(`Drawing triangle with base ${this.base.toFixed(1)} and height ${this.height.toFixed(1)}`);\n }\n\n getArea(): number {\n return 0.5 * this.base * this.height;\n }\n}\n\nclass Canvas {\n drawAll(shapes: Drawable[]): void {\n for (const shape of shapes) {\n shape.draw();\n console.log(` Area: ${shape.getArea().toFixed(2)}\\n`);\n }\n }\n}\n\nconst canvas = new Canvas();\n\nconst shapes: Drawable[] = [\n new Circle(5.0),\n new Rectangle(4.0, 6.0),\n new Triangle(3.0, 8.0),\n];\n\ncanvas.drawAll(shapes);\n```\n\n\n---\n\n# Exercise 2: Plugin System\n\n\n**Problem:** Build a text editor plugin system. A `Plugin` interface defines what every plugin can do, and a `TextEditor` loads and runs plugins through the interface without knowing their concrete types.\n\n**Requirements:**\n\n- `Plugin` interface with `execute(text)` that returns the processed text, and `getName()` that returns the plugin name.\n- `SpellCheckPlugin` that converts common misspellings (e.g., \"teh\" to \"the\").\n- `WordCountPlugin` that appends a word count to the text.\n- `UpperCasePlugin` that converts text to uppercase.\n- `TextEditor` with `registerPlugin(plugin)` and `runPlugins(text)` methods. It stores plugins as a list of `Plugin` references and runs them in sequence.\n\n```java\nimport java.util.List;\nimport java.util.ArrayList;\n\ninterface Plugin {\n String execute(String text);\n String getName();\n}\n\nclass SpellCheckPlugin implements Plugin {\n public String execute(String text) {\n // TODO: replace \"teh\" with \"the\", \"adn\" with \"and\"\n return text;\n }\n\n public String getName() {\n return \"Spell Check\";\n }\n}\n\nclass WordCountPlugin implements Plugin {\n public String execute(String text) {\n // TODO: append \"\\n[Word count: X]\" to the text\n return text;\n }\n\n public String getName() {\n return \"Word Count\";\n }\n}\n\nclass UpperCasePlugin implements Plugin {\n public String execute(String text) {\n // TODO: return text.toUpperCase()\n return text;\n }\n\n public String getName() {\n return \"Upper Case\";\n }\n}\n\nclass TextEditor {\n private List plugins = new ArrayList<>();\n\n public void registerPlugin(Plugin plugin) {\n // TODO: Add the plugin to the list and print \"Registered: [name]\"\n }\n\n public String runPlugins(String text) {\n // TODO: Run each plugin in sequence, passing output of one as input to the next\n // Print \"Running: [name]\" before each plugin\n // Return the final processed text\n return text;\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n TextEditor editor = new TextEditor();\n editor.registerPlugin(new SpellCheckPlugin());\n editor.registerPlugin(new WordCountPlugin());\n\n String result = editor.runPlugins(\"teh quick brown fox adn teh lazy dog\");\n System.out.println(\"\\nFinal output: \" + result);\n }\n}\n```\n\n```python\nfrom abc import ABC, abstractmethod\n\nclass Plugin(ABC):\n @abstractmethod\n def execute(self, text):\n pass\n\n @abstractmethod\n def get_name(self):\n pass\n\nclass SpellCheckPlugin(Plugin):\n def execute(self, text):\n return text # TODO: replace \"teh\" with \"the\", \"adn\" with \"and\"\n\n def get_name(self):\n return \"Spell Check\"\n\nclass WordCountPlugin(Plugin):\n def execute(self, text):\n return text # TODO: append \"\\n[Word count: X]\" to the text\n\n def get_name(self):\n return \"Word Count\"\n\nclass UpperCasePlugin(Plugin):\n def execute(self, text):\n return text # TODO: return text.upper()\n\n def get_name(self):\n return \"Upper Case\"\n\nclass TextEditor:\n def __init__(self):\n self.plugins = []\n\n def register_plugin(self, plugin):\n # TODO: Add the plugin to the list and print \"Registered: [name]\"\n pass\n\n def run_plugins(self, text):\n # TODO: Run each plugin in sequence, passing output of one as input to the next\n # Print \"Running: [name]\" before each plugin\n # Return the final processed text\n return text\n\nif __name__ == \"__main__\":\n editor = TextEditor()\n editor.register_plugin(SpellCheckPlugin())\n editor.register_plugin(WordCountPlugin())\n\n result = editor.run_plugins(\"teh quick brown fox adn teh lazy dog\")\n print(f\"\\nFinal output: {result}\")\n```\n\n```cpp\n#include \n#include \n#include \n#include \n#include \n#include \nusing namespace std;\n\nclass Plugin {\npublic:\n virtual string execute(const string& text) = 0;\n virtual string getName() = 0;\n virtual ~Plugin() = default;\n};\n\nclass SpellCheckPlugin : public Plugin {\npublic:\n string execute(const string& text) override {\n // TODO: replace \"teh\" with \"the\", \"adn\" with \"and\"\n return text;\n }\n\n string getName() override {\n return \"Spell Check\";\n }\n};\n\nclass WordCountPlugin : public Plugin {\npublic:\n string execute(const string& text) override {\n // TODO: append \"\\n[Word count: X]\" to the text\n return text;\n }\n\n string getName() override {\n return \"Word Count\";\n }\n};\n\nclass UpperCasePlugin : public Plugin {\npublic:\n string execute(const string& text) override {\n // TODO: return text in uppercase\n return text;\n }\n\n string getName() override {\n return \"Upper Case\";\n }\n};\n\nclass TextEditor {\n vector> plugins;\n\npublic:\n void registerPlugin(unique_ptr plugin) {\n // TODO: Add the plugin to the list and print \"Registered: [name]\"\n }\n\n string runPlugins(const string& text) {\n // TODO: Run each plugin in sequence, passing output of one as input to the next\n // Print \"Running: [name]\" before each plugin\n // Return the final processed text\n return text;\n }\n};\n\nint main() {\n TextEditor editor;\n editor.registerPlugin(make_unique());\n editor.registerPlugin(make_unique());\n\n string result = editor.runPlugins(\"teh quick brown fox adn teh lazy dog\");\n cout << \"\\nFinal output: \" << result << endl;\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport \"fmt\"\n\ntype Plugin interface {\n\tExecute(text string) string\n\tGetName() string\n}\n\ntype SpellCheckPlugin struct{}\n\nfunc (p *SpellCheckPlugin) Execute(text string) string {\n\t// TODO: replace \"teh\" with \"the\", \"adn\" with \"and\"\n\treturn text\n}\n\nfunc (p *SpellCheckPlugin) GetName() string {\n\treturn \"Spell Check\"\n}\n\ntype WordCountPlugin struct{}\n\nfunc (p *WordCountPlugin) Execute(text string) string {\n\t// TODO: append \"\\n[Word count: X]\" to the text\n\treturn text\n}\n\nfunc (p *WordCountPlugin) GetName() string {\n\treturn \"Word Count\"\n}\n\ntype UpperCasePlugin struct{}\n\nfunc (p *UpperCasePlugin) Execute(text string) string {\n\t// TODO: return text.toUpperCase()\n\treturn text\n}\n\nfunc (p *UpperCasePlugin) GetName() string {\n\treturn \"Upper Case\"\n}\n\ntype TextEditor struct {\n\tplugins []Plugin\n}\n\nfunc (t *TextEditor) RegisterPlugin(plugin Plugin) {\n\t// TODO: Add the plugin to the list and print \"Registered: [name]\"\n}\n\nfunc (t *TextEditor) RunPlugins(text string) string {\n\t// TODO: Run each plugin in sequence, passing output of one as input to the next\n\t// Print \"Running: [name]\" before each plugin\n\t// Return the final processed text\n\treturn text\n}\n\nfunc main() {\n\teditor := &TextEditor{}\n\teditor.RegisterPlugin(&SpellCheckPlugin{})\n\teditor.RegisterPlugin(&WordCountPlugin{})\n\n\tresult := editor.RunPlugins(\"teh quick brown fox adn teh lazy dog\")\n\tfmt.Printf(\"\\nFinal output: %s\\n\", result)\n}\n```\n\n```csharp\nusing System;\nusing System.Collections.Generic;\n\ninterface IPlugin\n{\n string Execute(string text);\n string GetName();\n}\n\nclass SpellCheckPlugin : IPlugin\n{\n public string Execute(string text)\n {\n // TODO: replace \"teh\" with \"the\", \"adn\" with \"and\"\n return text;\n }\n\n public string GetName() => \"Spell Check\";\n}\n\nclass WordCountPlugin : IPlugin\n{\n public string Execute(string text)\n {\n // TODO: append \"\\n[Word count: X]\" to the text\n return text;\n }\n\n public string GetName() => \"Word Count\";\n}\n\nclass UpperCasePlugin : IPlugin\n{\n public string Execute(string text)\n {\n // TODO: return text.ToUpper()\n return text;\n }\n\n public string GetName() => \"Upper Case\";\n}\n\nclass TextEditor\n{\n private List plugins = new List();\n\n public void RegisterPlugin(IPlugin plugin)\n {\n // TODO: Add the plugin to the list and print \"Registered: [name]\"\n }\n\n public string RunPlugins(string text)\n {\n // TODO: Run each plugin in sequence, passing output of one as input to the next\n // Print \"Running: [name]\" before each plugin\n // Return the final processed text\n return text;\n }\n}\n\nclass Program\n{\n static void Main()\n {\n var editor = new TextEditor();\n editor.RegisterPlugin(new SpellCheckPlugin());\n editor.RegisterPlugin(new WordCountPlugin());\n\n string result = editor.RunPlugins(\"teh quick brown fox adn teh lazy dog\");\n Console.WriteLine($\"\\nFinal output: {result}\");\n }\n}\n```\n\n```typescript\ninterface Plugin {\n execute(text: string): string;\n getName(): string;\n}\n\nclass SpellCheckPlugin implements Plugin {\n execute(text: string): string {\n // TODO: replace \"teh\" with \"the\", \"adn\" with \"and\"\n return text;\n }\n\n getName(): string {\n return \"Spell Check\";\n }\n}\n\nclass WordCountPlugin implements Plugin {\n execute(text: string): string {\n // TODO: append \"\\n[Word count: X]\" to the text\n return text;\n }\n\n getName(): string {\n return \"Word Count\";\n }\n}\n\nclass UpperCasePlugin implements Plugin {\n execute(text: string): string {\n // TODO: return text.toUpperCase()\n return text;\n }\n\n getName(): string {\n return \"Upper Case\";\n }\n}\n\nclass TextEditor {\n private plugins: Plugin[] = [];\n\n registerPlugin(plugin: Plugin): void {\n // TODO: Add the plugin to the list and print \"Registered: [name]\"\n }\n\n runPlugins(text: string): string {\n // TODO: Run each plugin in sequence, passing output of one as input to the next\n // Print \"Running: [name]\" before each plugin\n // Return the final processed text\n return text;\n }\n}\n\nconst editor = new TextEditor();\neditor.registerPlugin(new SpellCheckPlugin());\neditor.registerPlugin(new WordCountPlugin());\n\nconst result = editor.runPlugins(\"teh quick brown fox adn teh lazy dog\");\nconsole.log(`\\nFinal output: ${result}`);\n```\n\n#### Solutions\n\n```java\nimport java.util.List;\nimport java.util.ArrayList;\n\ninterface Plugin {\n String execute(String text);\n String getName();\n}\n\nclass SpellCheckPlugin implements Plugin {\n public String execute(String text) {\n return text.replace(\"teh\", \"the\").replace(\"adn\", \"and\");\n }\n\n public String getName() {\n return \"Spell Check\";\n }\n}\n\nclass WordCountPlugin implements Plugin {\n public String execute(String text) {\n int count = text.trim().split(\"\\\\s+\").length;\n return text + \"\\n[Word count: \" + count + \"]\";\n }\n\n public String getName() {\n return \"Word Count\";\n }\n}\n\nclass UpperCasePlugin implements Plugin {\n public String execute(String text) {\n return text.toUpperCase();\n }\n\n public String getName() {\n return \"Upper Case\";\n }\n}\n\nclass TextEditor {\n private List plugins = new ArrayList<>();\n\n public void registerPlugin(Plugin plugin) {\n plugins.add(plugin);\n System.out.println(\"Registered: \" + plugin.getName());\n }\n\n public String runPlugins(String text) {\n String result = text;\n for (Plugin plugin : plugins) {\n System.out.println(\"Running: \" + plugin.getName());\n result = plugin.execute(result);\n }\n return result;\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n TextEditor editor = new TextEditor();\n editor.registerPlugin(new SpellCheckPlugin());\n editor.registerPlugin(new WordCountPlugin());\n\n String result = editor.runPlugins(\"teh quick brown fox adn teh lazy dog\");\n System.out.println(\"\\nFinal output: \" + result);\n }\n}\n```\n\n```python\nfrom abc import ABC, abstractmethod\n\nclass Plugin(ABC):\n @abstractmethod\n def execute(self, text):\n pass\n\n @abstractmethod\n def get_name(self):\n pass\n\nclass SpellCheckPlugin(Plugin):\n def execute(self, text):\n return text.replace(\"teh\", \"the\").replace(\"adn\", \"and\")\n\n def get_name(self):\n return \"Spell Check\"\n\nclass WordCountPlugin(Plugin):\n def execute(self, text):\n count = len(text.strip().split())\n return text + f\"\\n[Word count: {count}]\"\n\n def get_name(self):\n return \"Word Count\"\n\nclass UpperCasePlugin(Plugin):\n def execute(self, text):\n return text.upper()\n\n def get_name(self):\n return \"Upper Case\"\n\nclass TextEditor:\n def __init__(self):\n self.plugins = []\n\n def register_plugin(self, plugin):\n self.plugins.append(plugin)\n print(f\"Registered: {plugin.get_name()}\")\n\n def run_plugins(self, text):\n result = text\n for plugin in self.plugins:\n print(f\"Running: {plugin.get_name()}\")\n result = plugin.execute(result)\n return result\n\nif __name__ == \"__main__\":\n editor = TextEditor()\n editor.register_plugin(SpellCheckPlugin())\n editor.register_plugin(WordCountPlugin())\n\n result = editor.run_plugins(\"teh quick brown fox adn teh lazy dog\")\n print(f\"\\nFinal output: {result}\")\n```\n\n```cpp\n#include \n#include \n#include \n#include \n#include \n#include \nusing namespace std;\n\nclass Plugin {\npublic:\n virtual string execute(const string& text) = 0;\n virtual string getName() = 0;\n virtual ~Plugin() = default;\n};\n\nclass SpellCheckPlugin : public Plugin {\npublic:\n string execute(const string& text) override {\n string result = text;\n size_t pos;\n while ((pos = result.find(\"teh\")) != string::npos) {\n result.replace(pos, 3, \"the\");\n }\n while ((pos = result.find(\"adn\")) != string::npos) {\n result.replace(pos, 3, \"and\");\n }\n return result;\n }\n\n string getName() override {\n return \"Spell Check\";\n }\n};\n\nclass WordCountPlugin : public Plugin {\npublic:\n string execute(const string& text) override {\n istringstream stream(text);\n string word;\n int count = 0;\n while (stream >> word) {\n count++;\n }\n return text + \"\\n[Word count: \" + to_string(count) + \"]\";\n }\n\n string getName() override {\n return \"Word Count\";\n }\n};\n\nclass UpperCasePlugin : public Plugin {\npublic:\n string execute(const string& text) override {\n string result = text;\n transform(result.begin(), result.end(), result.begin(), ::toupper);\n return result;\n }\n\n string getName() override {\n return \"Upper Case\";\n }\n};\n\nclass TextEditor {\n vector> plugins;\n\npublic:\n void registerPlugin(unique_ptr plugin) {\n cout << \"Registered: \" << plugin->getName() << endl;\n plugins.push_back(move(plugin));\n }\n\n string runPlugins(const string& text) {\n string result = text;\n for (auto& plugin : plugins) {\n cout << \"Running: \" << plugin->getName() << endl;\n result = plugin->execute(result);\n }\n return result;\n }\n};\n\nint main() {\n TextEditor editor;\n editor.registerPlugin(make_unique());\n editor.registerPlugin(make_unique());\n\n string result = editor.runPlugins(\"teh quick brown fox adn teh lazy dog\");\n cout << \"\\nFinal output: \" << result << endl;\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport (\n\t\"fmt\"\n\t\"strings\"\n)\n\ntype Plugin interface {\n\tExecute(text string) string\n\tGetName() string\n}\n\ntype SpellCheckPlugin struct{}\n\nfunc (p SpellCheckPlugin) Execute(text string) string {\n\treturn strings.ReplaceAll(strings.ReplaceAll(text, \"teh\", \"the\"), \"adn\", \"and\")\n}\n\nfunc (p SpellCheckPlugin) GetName() string {\n\treturn \"Spell Check\"\n}\n\ntype WordCountPlugin struct{}\n\nfunc (p WordCountPlugin) Execute(text string) string {\n\tfields := strings.Fields(text)\n\tcount := len(fields)\n\treturn fmt.Sprintf(\"%s\\n[Word count: %d]\", text, count)\n}\n\nfunc (p WordCountPlugin) GetName() string {\n\treturn \"Word Count\"\n}\n\ntype UpperCasePlugin struct{}\n\nfunc (p UpperCasePlugin) Execute(text string) string {\n\treturn strings.ToUpper(text)\n}\n\nfunc (p UpperCasePlugin) GetName() string {\n\treturn \"Upper Case\"\n}\n\ntype TextEditor struct {\n\tplugins []Plugin\n}\n\nfunc NewTextEditor() *TextEditor {\n\treturn &TextEditor{\n\t\tplugins: make([]Plugin, 0),\n\t}\n}\n\nfunc (e *TextEditor) RegisterPlugin(plugin Plugin) {\n\te.plugins = append(e.plugins, plugin)\n\tfmt.Printf(\"Registered: %s\\n\", plugin.GetName())\n}\n\nfunc (e *TextEditor) RunPlugins(text string) string {\n\tresult := text\n\tfor _, plugin := range e.plugins {\n\t\tfmt.Printf(\"Running: %s\\n\", plugin.GetName())\n\t\tresult = plugin.Execute(result)\n\t}\n\treturn result\n}\n\nfunc main() {\n\teditor := NewTextEditor()\n\teditor.RegisterPlugin(SpellCheckPlugin{})\n\teditor.RegisterPlugin(WordCountPlugin{})\n\n\tresult := editor.RunPlugins(\"teh quick brown fox adn teh lazy dog\")\n\tfmt.Printf(\"\\nFinal output: %s\\n\", result)\n}\n```\n\n```csharp\nusing System;\nusing System.Collections.Generic;\n\ninterface IPlugin\n{\n string Execute(string text);\n string GetName();\n}\n\nclass SpellCheckPlugin : IPlugin\n{\n public string Execute(string text)\n {\n return text.Replace(\"teh\", \"the\").Replace(\"adn\", \"and\");\n }\n\n public string GetName() => \"Spell Check\";\n}\n\nclass WordCountPlugin : IPlugin\n{\n public string Execute(string text)\n {\n int count = text.Trim().Split(new[] { ' ' },\n StringSplitOptions.RemoveEmptyEntries).Length;\n return text + $\"\\n[Word count: {count}]\";\n }\n\n public string GetName() => \"Word Count\";\n}\n\nclass UpperCasePlugin : IPlugin\n{\n public string Execute(string text)\n {\n return text.ToUpper();\n }\n\n public string GetName() => \"Upper Case\";\n}\n\nclass TextEditor\n{\n private List plugins = new List();\n\n public void RegisterPlugin(IPlugin plugin)\n {\n plugins.Add(plugin);\n Console.WriteLine($\"Registered: {plugin.GetName()}\");\n }\n\n public string RunPlugins(string text)\n {\n string result = text;\n foreach (var plugin in plugins)\n {\n Console.WriteLine($\"Running: {plugin.GetName()}\");\n result = plugin.Execute(result);\n }\n return result;\n }\n}\n\nclass Program\n{\n static void Main()\n {\n var editor = new TextEditor();\n editor.RegisterPlugin(new SpellCheckPlugin());\n editor.RegisterPlugin(new WordCountPlugin());\n\n string result = editor.RunPlugins(\"teh quick brown fox adn teh lazy dog\");\n Console.WriteLine($\"\\nFinal output: {result}\");\n }\n}\n```\n\n```typescript\ninterface Plugin {\n execute(text: string): string;\n getName(): string;\n}\n\nclass SpellCheckPlugin implements Plugin {\n execute(text: string): string {\n return text.replace(/teh/g, \"the\").replace(/adn/g, \"and\");\n }\n\n getName(): string {\n return \"Spell Check\";\n }\n}\n\nclass WordCountPlugin implements Plugin {\n execute(text: string): string {\n const count = text.trim().split(/\\s+/).length;\n return text + `\\n[Word count: ${count}]`;\n }\n\n getName(): string {\n return \"Word Count\";\n }\n}\n\nclass UpperCasePlugin implements Plugin {\n execute(text: string): string {\n return text.toUpperCase();\n }\n\n getName(): string {\n return \"Upper Case\";\n }\n}\n\nclass TextEditor {\n private plugins: Plugin[] = [];\n\n registerPlugin(plugin: Plugin): void {\n this.plugins.push(plugin);\n console.log(`Registered: ${plugin.getName()}`);\n }\n\n runPlugins(text: string): string {\n let result = text;\n for (const plugin of this.plugins) {\n console.log(`Running: ${plugin.getName()}`);\n result = plugin.execute(result);\n }\n return result;\n }\n}\n\nconst editor = new TextEditor();\neditor.registerPlugin(new SpellCheckPlugin());\neditor.registerPlugin(new WordCountPlugin());\n\nconst result = editor.runPlugins(\"teh quick brown fox adn teh lazy dog\");\nconsole.log(`\\nFinal output: ${result}`);\n```\n","pageType":"lld-interviews"}

Exercise: Realization

Exercise 1: Shape Drawing System

Exercise 2: Plugin System

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