Implement a Stack by using Queue

Question

This is reversed problem of 13. Implement a Queue by using Stack

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() // 5, now the array is [1, 2, 3, 4]

Above code is a Stack, while below is a Queue

const arr = [1, 2, 3, 4]

arr.push(5) // now the array is [1, 2, 3, 4, 5]
arr.shift() // 1, now the array is [2, 3, 4, 5]

now suppose you have a Queue, which has only follow interface:

class Queue {
  enqueue(element) { /* add element to queue, similar to Array.prototype.push */ }
  peek() { /* get the head element*/ }
  dequeue() { /* remove the head element, similar to Array.prototype.pop */ }
  size() { /* count of elements */ }
}

Could you implement a Stack by using only above Queue? A Stack must have following interface

class Stack {
  push(element) { /* add element to stack */ }
  peek() { /* get the top element */ }
  pop() { /* remove the top element */}
  size() { /* count of elements */}
}

note

you can only use Queue as provided. Don't use Array, it is not what this is for.

Code

/* you can use this Queue which is bundled together with your code
class Queue {
  enqueue(element) {
    // add new element to the queue
  }
  peek() { 
    // return the head element
  }
  dequeue() { 
    // remove head element from the queue
  }
  size() { 
    // return the queue size
  }
}
*/


// you need to complete the following Stack, using only Queue
class Stack {
  push(element) {
    // push an element into the stack
  }
  peek() { 
    // get the top element 
  }
  pop() { 
    // remove top element from stack
  }
  size() { 
    // return count of elements
  }
}

Related

• Implement a Queue by using Stack

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