stack implemented with linked list

Author: amejiarosario

lib/data-structures/stacks/stack-1.js

@@ -0,0 +1,40 @@
+/**
+ * Data structure that adds and remove elements in a last-in, first-out (LIFO) fashion
+ */
+class Stack {
+  constructor() {
+    this.input = [];
+  }
+
+  /**
+   * Add element into the stack
+   * Runtime: O(1)
+   * @param {any} element
+   */
+  add(element) {
+    this.input.push(element);
+    return this;
+  }
+
+  /**
+   * Remove element from the stack
+   * Runtime: O(1)
+   */
+  remove() {
+    return this.input.pop();
+  }
+
+  /**
+   * Size of the queue
+   */
+  get size() {
+    return this.input.length;
+  }
+}
+
+// aliases
+Stack.prototype.push = Stack.prototype.add;
+Stack.prototype.pop = Stack.prototype.remove;
+
+module.exports = Stack;
+

lib/data-structures/stacks/stack.js

@@ -1,17 +1,42 @@
+const LinkedList = require('../linked-lists/linked-list');
+
+/**
+ * Data structure that adds and remove elements in a last-in, first-out (LIFO) fashion
+ */
 class Stack {
   constructor() {
-    this.input = [];
+    this.input = new LinkedList();
   }
 
-  push(element) {
-    this.input.push(element);
+  /**
+   * Add element into the stack
+   * Runtime: O(1)
+   * @param {any} element
+   */
+  add(element) {
+    this.input.addLast(element);
     return this;
   }
 
-  pop() {
-    return this.input.pop();
+  /**
+   * Remove element from the stack
+   * Runtime: O(1)
+   */
+  remove() {
+    return this.input.removeLast();
+  }
+
+  /**
+   * Size of the queue
+   */
+  get size() {
+    return this.input.size;
   }
 }
 
+// aliases
+Stack.prototype.push = Stack.prototype.add;
+Stack.prototype.pop = Stack.prototype.remove;
+
 module.exports = Stack;
 

lib/data-structures/stacks/stack.spec.js

@@ -9,8 +9,9 @@ describe('Stack', function () {
 
   describe('#push', () => {
     it('should push an element to the stack', () => {
+      expect(stack.size).toEqual(0);
       stack.push(1);
-      expect(stack.input).toEqual([1]);
+      expect(stack.size).toEqual(1);
     });
   });
 
@@ -23,6 +24,7 @@ describe('Stack', function () {
     it('should get last element entered', () => {
       expect(stack.pop()).toEqual('b');
       expect(stack.pop()).toEqual('a');
+      expect(stack.pop()).toEqual(undefined);
     });
   });
 });