diff --git a/CHANGELOG.md b/CHANGELOG.md
index 921159b..5837ce7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,7 @@ All notable changes to this project will be documented in this file.
 - [Semantic Versioning](https://semver.org/spec/v2.0.0.html)
 - [`auto-changelog`](https://github.com/CookPete/auto-changelog)
 
-## [v1.54.3](https://github.com/zrwusa/data-structure-typed/compare/v1.51.5...main) (upcoming)
+## [v2.0.0](https://github.com/zrwusa/data-structure-typed/compare/v1.51.5...main) (upcoming)
 
 ### Changes
 
diff --git a/package-lock.json b/package-lock.json
index 562f4dc..73ebc20 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "data-structure-typed",
-  "version": "1.54.3",
+  "version": "2.0.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "data-structure-typed",
-      "version": "1.54.3",
+      "version": "2.0.0",
       "license": "MIT",
       "devDependencies": {
         "@eslint/compat": "^1.2.2",
diff --git a/src/data-structures/hash/hash-map.ts b/src/data-structures/hash/hash-map.ts
index 66334d0..08b70ce 100644
--- a/src/data-structures/hash/hash-map.ts
+++ b/src/data-structures/hash/hash-map.ts
@@ -21,6 +21,52 @@ import { isWeakKey, rangeCheck } from '../../utils';
  * 3. Unique Keys: Keys are unique.
  * If you try to insert another entry with the same key, the new one will replace the old entry.
  * 4. Unordered Collection: HashMap does not guarantee the order of entries, and the order may change over time.
+ * @example
+ * // should maintain insertion order
+ *     const linkedHashMap = new LinkedHashMap<number, string>();
+ *     linkedHashMap.set(1, 'A');
+ *     linkedHashMap.set(2, 'B');
+ *     linkedHashMap.set(3, 'C');
+ *
+ *     const result = Array.from(linkedHashMap);
+ *     console.log(result); // [
+ *  //      [1, 'A'],
+ *  //      [2, 'B'],
+ *  //      [3, 'C']
+ *  //    ]
+ * @example
+ * // fast lookup of values by key
+ *     const hashMap = new HashMap<number, string>();
+ *     hashMap.set(1, 'A');
+ *     hashMap.set(2, 'B');
+ *     hashMap.set(3, 'C');
+ *
+ *     console.log(hashMap.get(1)); // 'A'
+ *     console.log(hashMap.get(2)); // 'B'
+ *     console.log(hashMap.get(3)); // 'C'
+ *     console.log(hashMap.get(99)); // undefined
+ * @example
+ * // remove duplicates when adding multiple entries
+ *     const hashMap = new HashMap<number, string>();
+ *     hashMap.set(1, 'A');
+ *     hashMap.set(2, 'B');
+ *     hashMap.set(1, 'C'); // Update value for key 1
+ *
+ *     console.log(hashMap.size); // 2
+ *     console.log(hashMap.get(1)); // 'C'
+ *     console.log(hashMap.get(2)); // 'B'
+ * @example
+ * // count occurrences of keys
+ *     const data = [1, 2, 1, 3, 2, 1];
+ *
+ *     const countMap = new HashMap<number, number>();
+ *     for (const key of data) {
+ *       countMap.set(key, (countMap.get(key) || 0) + 1);
+ *     }
+ *
+ *     console.log(countMap.get(1)); // 3
+ *     console.log(countMap.get(2)); // 2
+ *     console.log(countMap.get(3)); // 1
  */
 export class HashMap<K = any, V = any, R = [K, V]> extends IterableEntryBase<K, V> {
   /**
diff --git a/src/data-structures/queue/queue.ts b/src/data-structures/queue/queue.ts
index 4b1da3c..da012cf 100644
--- a/src/data-structures/queue/queue.ts
+++ b/src/data-structures/queue/queue.ts
@@ -15,6 +15,53 @@ import { LinearBase } from '../base/linear-base';
  * 5. Data Buffering: Acting as a buffer for data packets in network communication.
  * 6. Breadth-First Search (BFS): In traversal algorithms for graphs and trees, queues store elements that are to be visited.
  * 7. Real-time Queuing: Like queuing systems in banks or supermarkets.
+ * @example
+ * // Sliding Window using Queue
+ *     const nums = [2, 3, 4, 1, 5];
+ *     const k = 2;
+ *     const queue = new Queue<number>();
+ *
+ *     let maxSum = 0;
+ *     let currentSum = 0;
+ *
+ *     nums.forEach((num, i) => {
+ *       queue.push(num);
+ *       currentSum += num;
+ *
+ *       if (queue.length > k) {
+ *         currentSum -= queue.shift()!;
+ *       }
+ *
+ *       if (queue.length === k) {
+ *         maxSum = Math.max(maxSum, currentSum);
+ *       }
+ *     });
+ *
+ *     console.log(maxSum); // 7
+ * @example
+ * // Breadth-First Search (BFS) using Queue
+ *     const graph: { [key in number]: number[] } = {
+ *       1: [2, 3],
+ *       2: [4, 5],
+ *       3: [],
+ *       4: [],
+ *       5: []
+ *     };
+ *
+ *     const queue = new Queue<number>();
+ *     const visited: number[] = [];
+ *
+ *     queue.push(1);
+ *
+ *     while (!queue.isEmpty()) {
+ *       const node = queue.shift()!;
+ *       if (!visited.includes(node)) {
+ *         visited.push(node);
+ *         graph[node].forEach(neighbor => queue.push(neighbor));
+ *       }
+ *     }
+ *
+ *     console.log(visited); // [1, 2, 3, 4, 5]
  */
 export class Queue<E = any, R = any> extends LinearBase<E, R> {
   constructor(elements: Iterable<E> | Iterable<R> = [], options?: QueueOptions<E, R>) {
diff --git a/test/unit/data-structures/binary-tree/avl-tree.test.ts b/test/unit/data-structures/binary-tree/avl-tree.test.ts
index ac3477c..7e3dfab 100644
--- a/test/unit/data-structures/binary-tree/avl-tree.test.ts
+++ b/test/unit/data-structures/binary-tree/avl-tree.test.ts
@@ -1,4 +1,4 @@
-import { AVLTree, AVLTreeNode, BinaryTreeNode, BSTNode, Range } from '../../../../src';
+import { AVLTree, AVLTreeNode, BinaryTreeNode, BSTNode } from '../../../../src';
 
 describe('AVL Tree Test', () => {
   it('should perform various operations on a AVL Tree', () => {
diff --git a/test/unit/data-structures/binary-tree/red-black-tree.test.ts b/test/unit/data-structures/binary-tree/red-black-tree.test.ts
index 43a12ca..c1bbf5c 100644
--- a/test/unit/data-structures/binary-tree/red-black-tree.test.ts
+++ b/test/unit/data-structures/binary-tree/red-black-tree.test.ts
@@ -1,4 +1,4 @@
-import { BinaryTreeNode, BSTNode, Range, RedBlackTree, RedBlackTreeNode } from '../../../../src';
+import { BinaryTreeNode, BSTNode, RedBlackTree, RedBlackTreeNode } from '../../../../src';
 import { getRandomInt, getRandomIntArray, magnitude } from '../../../utils';
 import { OrderedMap } from 'js-sdsl';
 
diff --git a/test/unit/data-structures/binary-tree/tree-multi-map.test.ts b/test/unit/data-structures/binary-tree/tree-multi-map.test.ts
index 394504c..08ba951 100644
--- a/test/unit/data-structures/binary-tree/tree-multi-map.test.ts
+++ b/test/unit/data-structures/binary-tree/tree-multi-map.test.ts
@@ -1,4 +1,4 @@
-import { BinaryTreeNode, BSTNode, Range, TreeMultiMap, TreeMultiMapNode } from '../../../../src';
+import { BinaryTreeNode, BSTNode, TreeMultiMap, TreeMultiMapNode } from '../../../../src';
 import { getRandomInt } from '../../../utils';
 
 import { isDebugTest } from '../../../config';
diff --git a/test/unit/data-structures/hash/hash-map.test.ts b/test/unit/data-structures/hash/hash-map.test.ts
index 510edb9..dd04762 100644
--- a/test/unit/data-structures/hash/hash-map.test.ts
+++ b/test/unit/data-structures/hash/hash-map.test.ts
@@ -842,3 +842,138 @@ describe('LinkedHashMap', () => {
     });
   });
 });
+
+describe('classic uses', () => {
+  it('@example should maintain insertion order', () => {
+    const linkedHashMap = new LinkedHashMap<number, string>();
+    linkedHashMap.set(1, 'A');
+    linkedHashMap.set(2, 'B');
+    linkedHashMap.set(3, 'C');
+
+    const result = Array.from(linkedHashMap);
+    expect(result).toEqual([
+      [1, 'A'],
+      [2, 'B'],
+      [3, 'C']
+    ]);
+  });
+
+  it('should allow reverse iteration', () => {
+    const linkedHashMap = new LinkedHashMap<number, string>();
+    linkedHashMap.set(1, 'A');
+    linkedHashMap.set(2, 'B');
+    linkedHashMap.set(3, 'C');
+
+    const result = Array.from(linkedHashMap.reverseBegin());
+    expect(result).toEqual([
+      [3, 'C'],
+      [2, 'B'],
+      [1, 'A']
+    ]);
+  });
+
+  it('should allow fast deletion at an index', () => {
+    const linkedHashMap = new LinkedHashMap<number, string>();
+    linkedHashMap.set(1, 'A');
+    linkedHashMap.set(2, 'B');
+    linkedHashMap.set(3, 'C');
+
+    linkedHashMap.deleteAt(1);
+
+    const result = Array.from(linkedHashMap);
+    expect(result).toEqual([
+      [1, 'A'],
+      [3, 'C']
+    ]);
+  });
+
+  it('should filter entries correctly', () => {
+    const linkedHashMap = new LinkedHashMap<number, string>();
+    linkedHashMap.set(1, 'A');
+    linkedHashMap.set(2, 'B');
+    linkedHashMap.set(3, 'C');
+
+    const filteredMap = linkedHashMap.filter((key, value) => value !== 'B');
+
+    const result = Array.from(filteredMap);
+    expect(result).toEqual([
+      [1, 'A'],
+      [3, 'C']
+    ]);
+  });
+
+  it('should map entries to a new LinkedHashMap', () => {
+    const linkedHashMap = new LinkedHashMap<number, string>();
+    linkedHashMap.set(1, 'A');
+    linkedHashMap.set(2, 'B');
+
+    const mappedMap = linkedHashMap.map((key, value) => [value, key]);
+
+    const result = Array.from(mappedMap);
+    expect(result).toEqual([
+      ['A', 1],
+      ['B', 2]
+    ]);
+  });
+});
+
+describe('classic uses', () => {
+  it('@example fast lookup of values by key', () => {
+    const hashMap = new HashMap<number, string>();
+    hashMap.set(1, 'A');
+    hashMap.set(2, 'B');
+    hashMap.set(3, 'C');
+
+    expect(hashMap.get(1)).toBe('A');
+    expect(hashMap.get(2)).toBe('B');
+    expect(hashMap.get(3)).toBe('C');
+    expect(hashMap.get(99)).toBeUndefined(); // Key not present
+  });
+
+  it('@example remove duplicates when adding multiple entries', () => {
+    const hashMap = new HashMap<number, string>();
+    hashMap.set(1, 'A');
+    hashMap.set(2, 'B');
+    hashMap.set(1, 'C'); // Update value for key 1
+
+    expect(hashMap.size).toBe(2);
+    expect(hashMap.get(1)).toBe('C');
+    expect(hashMap.get(2)).toBe('B');
+  });
+
+  it('@example count occurrences of keys', () => {
+    const data = [1, 2, 1, 3, 2, 1];
+
+    const countMap = new HashMap<number, number>();
+    for (const key of data) {
+      countMap.set(key, (countMap.get(key) || 0) + 1);
+    }
+
+    expect(countMap.get(1)).toBe(3);
+    expect(countMap.get(2)).toBe(2);
+    expect(countMap.get(3)).toBe(1);
+  });
+
+  it('should group entries by a key-derived property', () => {
+    const entries = [
+      { id: 1, group: 'A' },
+      { id: 2, group: 'B' },
+      { id: 3, group: 'A' },
+      { id: 4, group: 'B' }
+    ];
+
+    const groupedMap = new HashMap<string, number[]>();
+
+    for (const entry of entries) {
+      const group = entry.group;
+      const id = entry.id;
+      if (!groupedMap.has(group)) {
+        groupedMap.set(group, []);
+      }
+      groupedMap.get(group)?.push(id);
+    }
+
+    expect(groupedMap.get('A')).toEqual([1, 3]);
+    expect(groupedMap.get('B')).toEqual([2, 4]);
+  });
+});
diff --git a/test/unit/data-structures/queue/queue.test.ts b/test/unit/data-structures/queue/queue.test.ts
index c02e687..7c7df34 100644
--- a/test/unit/data-structures/queue/queue.test.ts
+++ b/test/unit/data-structures/queue/queue.test.ts
@@ -454,3 +454,217 @@ describe('LinkedListQueue', () => {
     expect(cloned.length).toBe(2);
   });
 });
+
+describe('Queue', () => {
+  // Test queue initialization
+  it('should initialize correctly with no elements', () => {
+    const queue = new Queue();
+    expect(queue.isEmpty()).toBe(true);
+    expect(queue.length).toBe(0);
+    expect(queue.first).toBeUndefined();
+    expect(queue.last).toBeUndefined();
+  });
+
+  it('should initialize correctly with given elements', () => {
+    const queue = new Queue([1, 2, 3]);
+    expect(queue.length).toBe(3);
+    expect(queue.first).toBe(1);
+    expect(queue.last).toBe(3);
+  });
+
+  // Test push and pushMany
+  it('should add elements to the queue', () => {
+    const queue = new Queue<number>();
+    queue.push(1);
+    queue.push(2);
+    expect(queue.length).toBe(2);
+    expect(queue.first).toBe(1);
+    expect(queue.last).toBe(2);
+  });
+
+  it('should add multiple elements using pushMany', () => {
+    const queue = new Queue<number>();
+    queue.pushMany([1, 2, 3]);
+    expect(queue.length).toBe(3);
+    expect(queue.elements).toEqual([1, 2, 3]);
+  });
+
+  // Test shift
+  it('should remove the first element from the queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    const shifted = queue.shift();
+    expect(shifted).toBe(1);
+    expect(queue.length).toBe(2);
+    expect(queue.first).toBe(2);
+  });
+
+  // Test delete and deleteAt
+  it('should delete an element from the queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    const result = queue.delete(2);
+    expect(result).toBe(true);
+    expect(queue.elements).toEqual([1, 3]);
+  });
+
+  it('should delete an element at a specific index', () => {
+    const queue = new Queue([1, 2, 3]);
+    const deleted = queue.deleteAt(1);
+    expect(deleted).toBe(2);
+    expect(queue.elements).toEqual([1, 3]);
+  });
+
+  // Test at
+  it('should retrieve an element by index', () => {
+    const queue = new Queue([1, 2, 3]);
+    expect(queue.at(0)).toBe(1);
+    expect(queue.at(2)).toBe(3);
+  });
+
+  // Test reverse
+  it('should reverse the queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    queue.reverse();
+    expect(queue.elements).toEqual([3, 2, 1]);
+    expect(queue.first).toBe(3);
+    expect(queue.last).toBe(1);
+  });
+
+  // Test addAt
+  it('should add an element at a specific index', () => {
+    const queue = new Queue([1, 3]);
+    const result = queue.addAt(1, 2);
+    expect(result).toBe(true);
+    expect(queue.elements).toEqual([1, 2, 3]);
+  });
+
+  // Test setAt
+  it('should set an element at a specific index', () => {
+    const queue = new Queue([1, 2, 3]);
+    const result = queue.setAt(1, 10);
+    expect(result).toBe(true);
+    expect(queue.elements).toEqual([1, 10, 3]);
+  });
+
+  // Test clear
+  it('should clear the queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    queue.clear();
+    expect(queue.isEmpty()).toBe(true);
+    expect(queue.length).toBe(0);
+  });
+
+  // Test compact
+  it('should compact the queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    queue.shift();
+    queue.shift();
+    queue.compact();
+    expect(queue.elements).toEqual([3]);
+  });
+
+  // Test splice
+  it('should splice elements from the queue', () => {
+    const queue = new Queue([1, 2, 3, 4]);
+    const removed = queue.splice(1, 2);
+    expect(removed.elements).toEqual([2, 3]);
+    expect(queue.elements).toEqual([1, 4]);
+  });
+
+  // Test clone
+  it('should create a clone of the queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    const clone = queue.clone();
+    expect(clone.elements).toEqual(queue.elements);
+    clone.push(4);
+    expect(queue.elements).not.toContain(4);
+  });
+
+  // Test filter
+  it('should filter elements based on a predicate', () => {
+    const queue = new Queue([1, 2, 3, 4]);
+    const filtered = queue.filter(el => el % 2 === 0);
+    expect(filtered.elements).toEqual([2, 4]);
+  });
+
+  // Test map
+  it('should map elements to a new queue', () => {
+    const queue = new Queue([1, 2, 3]);
+    const mapped = queue.map(el => el * 2);
+    expect(mapped.elements).toEqual([2, 4, 6]);
+  });
+});
+
+describe('classic uses', () => {
+  it('@example Sliding Window using Queue', () => {
+    const nums = [2, 3, 4, 1, 5];
+    const k = 2;
+    const queue = new Queue<number>();
+
+    let maxSum = 0;
+    let currentSum = 0;
+
+    nums.forEach((num, i) => {
+      queue.push(num);
+      currentSum += num;
+
+      if (queue.length > k) {
+        currentSum -= queue.shift()!;
+      }
+
+      if (queue.length === k) {
+        maxSum = Math.max(maxSum, currentSum);
+      }
+    });
+
+    expect(maxSum).toBe(7); // Maximum sum is from subarray [3, 4].
+  });
+
+  it('@example Breadth-First Search (BFS) using Queue', () => {
+    const graph: { [key in number]: number[] } = {
+      1: [2, 3],
+      2: [4, 5],
+      3: [],
+      4: [],
+      5: []
+    };
+
+    const queue = new Queue<number>();
+    const visited: number[] = [];
+
+    queue.push(1);
+
+    while (!queue.isEmpty()) {
+      const node = queue.shift()!;
+      if (!visited.includes(node)) {
+        visited.push(node);
+        graph[node].forEach(neighbor => queue.push(neighbor));
+      }
+    }
+
+    expect(visited).toEqual([1, 2, 3, 4, 5]); // Expected BFS traversal order.
+  });
+
+  it('Task Scheduling using Queue', () => {
+    const tasks = ['A', 'A', 'A', 'B', 'B', 'B'];
+    const cooldown = 2;
+
+    const taskQueue = new Queue<string>();
+    const cooldownQueue = new Queue<string>();
+
+    for (const task of tasks) {
+      while (!cooldownQueue.isEmpty() && cooldownQueue.first === task) {
+        cooldownQueue.shift();
+        taskQueue.push('idle');
+      }
+
+      taskQueue.push(task);
+      cooldownQueue.push(task);
+      if (cooldownQueue.length > cooldown) {
+        cooldownQueue.shift();
+      }
+    }
+
+    const scheduled = taskQueue.elements;
+    expect(scheduled).toEqual(['A', 'idle', 'A', 'idle', 'A', 'B', 'B', 'idle', 'idle', 'B']);
+  });
+});
diff --git a/test/unit/data-structures/stack/stack.test.ts b/test/unit/data-structures/stack/stack.test.ts
index 1875298..57f811a 100644
--- a/test/unit/data-structures/stack/stack.test.ts
+++ b/test/unit/data-structures/stack/stack.test.ts
@@ -162,3 +162,168 @@ describe('Stack iterative methods', () => {
     }).toThrow('toElementFn must be a function type');
   });
 });
+
+describe('classic uses', () => {
+  it('@example Balanced Parentheses or Brackets', () => {
+    type ValidCharacters = ')' | '(' | ']' | '[' | '}' | '{';
+
+    const stack = new Stack<string>();
+    const input: ValidCharacters[] = '[({})]'.split('') as ValidCharacters[];
+    const matches: { [key in ValidCharacters]?: ValidCharacters } = { ')': '(', ']': '[', '}': '{' };
+    for (const char of input) {
+      if ('([{'.includes(char)) {
+        stack.push(char);
+      } else if (')]}'.includes(char)) {
+        if (stack.pop() !== matches[char]) {
+          fail('Parentheses are not balanced');
+        }
+      }
+    }
+    expect(stack.isEmpty()).toBe(true);
+  });
+
+  it('@example Expression Evaluation and Conversion', () => {
+    const stack = new Stack<number>();
+    const expression = [5, 3, '+']; // Equivalent to 5 + 3
+    expression.forEach(token => {
+      if (typeof token === 'number') {
+        stack.push(token);
+      } else {
+        const b = stack.pop()!;
+        const a = stack.pop()!;
+        stack.push(token === '+' ? a + b : 0); // Only handling '+' here
+      }
+    });
+    expect(stack.pop()).toBe(8);
+  });
+
+  it('@example Depth-First Search (DFS)', () => {
+    const stack = new Stack<number>();
+    const graph: { [key in number]: number[] } = { 1: [2, 3], 2: [4], 3: [5], 4: [], 5: [] };
+    const visited: number[] = [];
+    stack.push(1);
+    while (!stack.isEmpty()) {
+      const node = stack.pop()!;
+      if (!visited.includes(node)) {
+        visited.push(node);
+        graph[node].forEach(neighbor => stack.push(neighbor));
+      }
+    }
+    expect(visited).toEqual([1, 3, 5, 2, 4]); // Example DFS order
+  });
+
+  it('@example Backtracking Algorithms', () => {
+    const stack = new Stack<[number, number]>();
+    const maze = [
+      ['S', ' ', 'X'],
+      ['X', ' ', 'X'],
+      [' ', ' ', 'E']
+    ];
+    const start: [number, number] = [0, 0];
+    const end = [2, 2];
+    const directions = [
+      [0, 1], // To the right
+      [1, 0], // down
+      [0, -1], // left
+      [-1, 0] // up
+    ];
+
+    const visited = new Set<string>(); // Used to record visited nodes
+    stack.push(start);
+    const path: number[][] = [];
+
+    while (!stack.isEmpty()) {
+      const [x, y] = stack.pop()!;
+      if (visited.has(`${x},${y}`)) continue; // Skip already visited nodes
+      visited.add(`${x},${y}`);
+
+      path.push([x, y]);
+
+      if (x === end[0] && y === end[1]) {
+        break; // Find the end point and exit
+      }
+
+      for (const [dx, dy] of directions) {
+        const nx = x + dx;
+        const ny = y + dy;
+        if (
+          maze[nx]?.[ny] === ' ' || // feasible path
+          maze[nx]?.[ny] === 'E' // destination
+        ) {
+          stack.push([nx, ny]);
+        }
+      }
+    }
+
+    expect(path).toContainEqual(end);
+  });
+
+  it('@example Function Call Stack', () => {
+    const functionStack = new Stack<string>();
+    functionStack.push('main');
+    functionStack.push('foo');
+    functionStack.push('bar');
+    expect(functionStack.pop()).toBe('bar');
+    expect(functionStack.pop()).toBe('foo');
+    expect(functionStack.pop()).toBe('main');
+  });
+
+  it('@example Simplify File Paths', () => {
+    const stack = new Stack<string>();
+    const path = '/a/./b/../../c';
+    path.split('/').forEach(segment => {
+      if (segment === '..') stack.pop();
+      else if (segment && segment !== '.') stack.push(segment);
+    });
+    expect(stack.elements.join('/')).toBe('c');
+  });
+
+  it('@example Stock Span Problem', () => {
+    const stack = new Stack<number>();
+    const prices = [100, 80, 60, 70, 60, 75, 85];
+    const spans: number[] = [];
+    prices.forEach((price, i) => {
+      while (!stack.isEmpty() && prices[stack.peek()!] <= price) {
+        stack.pop();
+      }
+      spans.push(stack.isEmpty() ? i + 1 : i - stack.peek()!);
+      stack.push(i);
+    });
+    expect(spans).toEqual([1, 1, 1, 2, 1, 4, 6]);
+  });
+
+  it('Browser Navigation', () => {
+    const backStack = new Stack<string>();
+    const forwardStack = new Stack<string>();
+    backStack.push('Page 1');
+    backStack.push('Page 2');
+    forwardStack.push(backStack.pop()!);
+    expect(backStack.size).toBe(1);
+    expect(forwardStack.size).toBe(1);
+  });
+
+  it('String Reversal', () => {
+    const stack = new Stack<string>();
+    const input = 'hello';
+    const reversed = [];
+    input.split('').forEach(char => stack.push(char));
+    while (!stack.isEmpty()) {
+      reversed.push(stack.pop());
+    }
+    expect(reversed.join('')).toBe('olleh');
+  });
+
+  it('Next Greater Element', () => {
+    const stack = new Stack<number>();
+    const array = [4, 5, 2, 25];
+    const nextGreater = new Array(array.length).fill(-1);
+    array.forEach((_, i) => {
+      while (!stack.isEmpty() && array[stack.peek()!] < array[i]) {
+        const idx = stack.pop()!;
+        nextGreater[idx] = array[i];
+      }
+      stack.push(i);
+    });
+    expect(nextGreater).toEqual([5, 25, 25, -1]);
+  });
+});