Design-2

Problem 1: (https://leetcode.com/problems/implement-queue-using-stacks/)

Implement the following operations of a queue using stacks.

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

pop() -- Removes the element from in front of queue.

peek() -- Get the front element.

empty() -- Return whether the queue is empty.

Problem 2:(https://leetcode.com/problems/design-hashset/)

Design a HashSet without using any built-in hash table libraries. To be specific, your design should include these functions:

add(value): Insert a value into the HashSet.

contains(value) : Return whether the value exists in the HashSet or not.

remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.