--update: immitate Queue using 2 stacks

Author: ashokdey

src/_DataStructures_/Stack/immitate-queue-using-stack/immitate-queue-using-stack.test.js

@@ -0,0 +1,57 @@
+const Queue = require('.');
+
+describe('Immitated Queue using 2 Stacks', () => {
+  it('Should be class', () => {
+    expect(typeof Queue.prototype.constructor).toEqual('function');
+  });
+
+  describe('Queue API', () => {
+    let queue = null;
+
+    beforeEach(() => {
+      queue = new Queue();
+    });
+
+    it('Should add() element to a queue', () => {
+      queue.add(5);
+      expect(queue.data).toEqual([5]);
+    });
+
+    it('Should remove() an element from the queue', () => {
+      queue.add(2);
+      queue.add(3);
+
+      expect(queue.remove()).toEqual(2);
+      expect(queue.data).toEqual([3]);
+    });
+
+    describe('peek()', () => {
+      beforeEach(() => {
+        queue.add(2);
+        queue.add(5);
+      });
+
+      it('Should return the elemet to be removed using peek()', () => {
+        expect(queue.peek()).toEqual(2);
+      });
+
+      it('Should not remove the element', () => {
+        expect(queue.peek()).toEqual(2);
+        expect(queue.remove()).toEqual(2);
+      });
+    });
+
+    it('Should maintain the order of elements', () => {
+      // first in first out
+      queue.add(2);
+      queue.add(1);
+      queue.add(4);
+      queue.add(3);
+
+      expect(queue.remove()).toEqual(2);
+      expect(queue.remove()).toEqual(1);
+      expect(queue.remove()).toEqual(4);
+      expect(queue.remove()).toEqual(3);
+    });
+  });
+});

src/_DataStructures_/Stack/immitate-queue-using-stack/index.js

@@ -0,0 +1,45 @@
+const Stack = require('../index');
+
+class ImmitateQueue {
+  constructor() {
+    this.stackA = new Stack();
+    this.stackB = new Stack();
+    this.data = this.stackA.data;
+  }
+
+  add(element) {
+    this.stackA.push(element);
+    this.data = this.stackA.data;
+  }
+
+  peek() {
+    while (this.stackA.peek()) {
+      this.stackB.push(this.stackA.pop());
+    }
+
+    const element = this.stackB.peek();
+
+    while (this.stackB.peek()) {
+      this.stackA.push(this.stackB.pop());
+    }
+    this.data = this.stackA.data;
+    return element;
+  }
+
+  remove() {
+    while (this.stackA.peek()) {
+      this.stackB.push(this.stackA.pop());
+    }
+
+    const element = this.stackB.pop();
+
+    while (this.stackB.peek()) {
+      this.stackA.push(this.stackB.pop());
+    }
+
+    this.data = this.stackA.data;
+    return element;
+  }
+}
+
+module.exports = ImmitateQueue;