<pre class="shiki github-dark shaku"><code>/* you can use this Class which is bundled together with your codeclass Stack { push(element) { // add element to stack } peek() { // get the top element } pop() { // remove the top element} size() { // count of element }}*//* Array is disabled in your code */// you need to complete the following Classclass Queue { constructor(){ this.left = new Stack() this.right = new Stack() } enqueue(element) { // add new element to the rare this.left.push(element) } peek() { // get the head element // right size is zero then we need to push // all the elements to right, which will be reversed hence peek will work if(this.right.size()==0){ // right size is zero then we need to push all the elements to right, which will be reversed hence peek will work while(this.left.size()){ this.right.push(this.left.pop()) } } // always return right, as it will always have a value return this.right.peek() } size() { // return count of element // size is sum of left and right return this.left.size() + this.right.size() } dequeue() { // remove the head element if(this.right.size()==0){ while(this.left.size()){ this.right.push(this.left.pop()) } } return this.right.pop() }}class Queue1 { stack = new Stack(); enqueue(element) { // add new element to the rare const reversed = new Stack(); while(this.stack.size()){ reversed.push(this.stack.pop()); } reversed.push(element); while(reversed.size()){ this.stack.push(reversed.pop()); } } peek() { // get the head element return this.stack.peek(); } size() { // return count of element return this.stack.size(); } dequeue() { // remove the head element return this.stack.pop(); }}</code></pre>

Not Ideal but something interviewer will be looking for

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In JavaScript, we could use array to work as both a Stack or a queue. const arr = [1, 2, 3, 4]arr.push(5) // now array is [1, 2, 3, 4, 5]arr.pop() // …