### LeetCode Challenge #232. 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:

• `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.

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.
• 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.

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] (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.
##### Video Solution
###### Java Solution
```				```
class MyQueue {
private Stack<Integer> main;
private Stack<Integer> helper;

public MyQueue() {
main = new Stack<>();
helper = new Stack<>();
}

public void push(int x) {
// add all elements of main to helper -- main --> helper

while(main.size()>0){
helper.push(main.pop());
}

main.push(x);

// add all elemets from helper to main -- helper ---> main

while(helper.size()>0){
main.push(helper.pop());
}
}

public int pop() {
return main.pop();
}

public int peek() {
return main.peek();
}

public boolean empty() {
return main.size()==0;
}
}

/**
* Your MyQueue object will be instantiated and called as such:
* MyQueue obj = new MyQueue();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.peek();
* boolean param_4 = obj.empty();
*/
```
```