JavaScriptImplementQueueUsingStacks.md

JavaScript Implement Queue Using Stacks

Challenge

Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all the functions of a normal queue (push, peek, pop, and empty).

Implement the MyQueue class:

• void push(int x) Pushes element x to the back of the queue.
• int pop() Removes the element from the front of the queue and returns it.
• int peek() Returns the element at the front of the queue.
• boolean empty() Returns true if the queue is empty, false otherwise.

Note

Depending on your language, the stack may not be supported natively. You may simulate a stack using a list or deque (double-ended queue) as long as you use only a stack's standard operations.

Important

You must use only standard operations of a stack, which means only push to top, peek/pop from top, size, and is empty operations are valid.

Example

Input: ['MyQueue', 'push', 'push', 'peek', 'pop', 'empty']
[[], [1], [2], [], [], []]
Output: [null, null, null, 1, 1, false]
Explanation: MyQueue myQueue = new MyQueue();
myQueue.push(1); // queue is: [1]
myQueue.push(2); // queue is: [1, 2] (leftmost is front of the queue)
myQueue.peek(); // return 1
myQueue.pop(); // return 1, queue is [2]
myQueue.empty(); // return false

Constraints

• 1 <= x <= 9
• At most 100 calls will be made to push, pop, peek, and empty.
• All the calls to pop and peek are valid.

Solution

class MyQueue {
    data = [];

    constructor() {
        this.data = [];
    }

    push(x) {
        this.data.push(x);
    }

    pop() {
        const temp = this.data[0];
        let toReturn;

        if(this.data.length > 0) {
            toReturn = temp;
        }

        this.data.shift();

        return toReturn;
    }

    peek() {
        return this.data[0];
    }

    empty() {
        return this.data.length === 0;
    }
};

Explanation

I've built a class called MyQueue that represents a queue data structure. The class has several methods: push, pop, peek, and empty.

The constructor initializes the data array, which will be used to store the elements of the queue.

The push method takes a parameter x and adds the element to the end of the data array using the push function.

The pop method removes and returns the first element of the queue. It assigns the first element to a temporary variable called temp. If the queue is not empty (determined by checking the length of the data array), it assigns the value of temp to a variable called toReturn. It then removes the first element of the queue using the shift function of the array. Finally, it returns the value of toReturn.

The peek method returns the first element of the queue without removing it. It simply accesses the element at index 0 of the data array.

The empty method checks if the length of the data array is equal to zero. If it is, it returns true, indicating that the queue is empty. Otherwise, it returns false.

In summary, the MyQueue class provides methods to manipulate a queue data structure. It allows elements to be added to the end of the queue, removed from the front of the queue, accessed without removal, and checked for emptiness.

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