**Please use C++ for all thanks!**

1. Implment the following operations of a queue using stacks.

enqueue(x) -- Push element x to the back of queue.

dequeue() -- Removes the element from the front of queue.

peekFront() -- Get the front element.

isEmpty() -- Return whether the queue is empty

2. Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

3.Given a binary tree, return the inorder traversal of its nodes values using stack.

4. Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3, which represents the number 123. Find the total sum of all root-to-leaf numbers