Implement Queue using Stacks

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:

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

Notes:

• 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.

Examples

Example 1:

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]

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