feat: more examples and exercises from chapter 9

Author: damianobacci

chapter-9/01_stack.rb

@@ -0,0 +1,17 @@
+class Stack
+    def initialize
+        @data = []
+    end
+
+    def push(element)
+        @data << (element)
+    end
+
+    def pop
+        @data.pop
+    end
+
+    def read
+        @data.last
+    end
+end

chapter-9/01_stack.ts

@@ -0,0 +1,21 @@
+export interface IArrayLike<T> {
+    push(element: T): void;
+    pop(): T | undefined;
+    read(): T | undefined;
+}
+
+export class Stack<T> implements IArrayLike<T> {
+    private data: T[] = [];
+
+    push(element: T): void {
+        this.data.push(element);
+    }
+
+    pop(): T | undefined {
+        return this.data.pop();
+    }
+
+    read(): T | undefined {
+        return this.data[this.data.length - 1];
+    }
+}

chapter-9/02_linter.rb

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+require_relative '01_stack'
+
+class Linter
+    def initialize
+        @stack = Stack.new
+    end
+
+    def lint(text)
+        text.each_char do |char|
+            if is_opening_brace?(char)
+                @stack.push(char)
+            elsif is_closing_brace?(char)
+                popped_opening_brace = @stack.pop
+                if !popped_opening_brace
+                    return "#{char} doesn't have a matching opening brace"
+                end
+                if is_not_a_match(popped_opening_brace, char)
+                    return "#{char} has mismatched opening brace"
+                end
+            end
+        end
+        if @stack.read
+            return "#{@stack.read} doesn't have a matching closing brace"
+        end
+        return true
+    end
+
+    private
+
+    def is_opening_brace?(char)
+        ['(', '[', '{'].include?(char)
+    end
+
+    def is_closing_brace?(char)
+        [')', ']', '}'].include?(char)
+    end
+
+    def is_not_a_match(opening_brace, closing_brace)
+        closing_brace != {"(" => ")", "[" => "]", "{" => "}" }[opening_brace]
+    end
+end

chapter-9/03_queue.rb

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+class Queue
+    def initialize
+        @data = []
+    end
+
+    def enqueue(el)
+        @data << el
+    end
+
+    def dequeue
+        @data.shift
+    end
+
+    def read
+        @data.first
+    end
+end

chapter-9/03_queue.ts

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+import { IArrayLike } from "./01_stack";
+
+export class Queue<T> implements IArrayLike<T> {
+
+    private data: T[] = []
+
+    push(el: T) { // enqueue
+        this.data.push(el)
+    }
+
+    pop() { // dequeue
+        return this.data.shift()
+    }
+
+    read() {
+        return this.data[0]
+    }
+
+}

chapter-9/ex4.ts

@@ -0,0 +1,13 @@
+import { Stack } from "./01_stack";
+
+function reverseString(str: string): string {
+    const stack = new Stack<string>();
+    for (const char of str) {
+        stack.push(char);
+    }
+    let reversed = '';
+    for (let i = 0; i < str.length; i++) {
+        reversed += stack.pop()
+    }
+    return reversed;
+}