stack and queue

Author: amejiarosario

lib/data-structures/queues/queue-1.js

@@ -0,0 +1,15 @@
+class Queue {
+  constructor() {
+    this.input = [];
+  }
+
+  add(element) {
+    this.input.push(element);
+  }
+
+  remove() {
+    return this.input.shift();
+  }
+}
+
+module.exports = Queue;

lib/data-structures/queues/queue.js

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+class Queue {
+  constructor() {
+    this.input = [];
+    this.output = [];
+  }
+
+  add(element) {
+    this.input.push(element);
+  }
+
+  remove() {
+    if(!this.output.length) {
+      while(this.input.length) {
+        this.output.push(this.input.pop());
+      }
+    }
+    return this.output.pop();
+  }
+}
+
+module.exports = Queue;

lib/data-structures/queues/queue.spec.js

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+const Queue = require('./queue-1.js');
+
+describe('Queue', function () {
+  let queue;
+
+  beforeEach(() => {
+    queue = new Queue();
+  });
+
+  describe('#add', () => {
+    it('should push an element to the queue', () => {
+      queue.add(1);
+      expect(queue.input).toEqual([1]);
+    });
+  });
+
+  describe('#remove', () => {
+    beforeEach(() => {
+      queue.add('a');
+      queue.add('b');
+    });
+
+    it('should get last element entered', () => {
+      expect(queue.remove()).toEqual('a');
+      expect(queue.remove()).toEqual('b');
+    });
+
+    it('should keep the order after some addition', () => {
+      expect(queue.remove()).toEqual('a');
+      queue.add('c');
+      expect(queue.remove()).toEqual('b');
+      expect(queue.remove()).toEqual('c');
+      expect(queue.remove()).toBe(undefined);
+    })
+  });
+});

lib/data-structures/stacks/stack.js

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+class Stack {
+  constructor() {
+    this.input = [];
+  }
+
+  push(element) {
+    this.input.push(element);
+    return this;
+  }
+
+  pop() {
+    return this.input.pop();
+  }
+}
+
+module.exports = Stack;
+

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

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+const Stack = require('./stack.js');
+
+describe('Stack', function () {
+  let stack;
+
+  beforeEach(() => {
+    stack = new Stack();
+  });
+
+  describe('#push', () => {
+    it('should push an element to the stack', () => {
+      stack.push(1);
+      expect(stack.input).toEqual([1]);
+    });
+  });
+
+  describe('#pop', () => {
+    beforeEach(() => {
+      stack.push('a');
+      stack.push('b');
+    });
+
+    it('should get last element entered', () => {
+      expect(stack.pop()).toEqual('b');
+      expect(stack.pop()).toEqual('a');
+    });
+  });
+});