Stack - FILO data structure

• could be implemented with Array or LinkedList
• use helper stack to assist getMin, getMax, reverse, swap or replace element
• use stack to store the index of the element instead of the element itself
• use queue to implement stack(tmp queue & body queue, offer and poll, swap reference)

Queue - FILO data structure

• could be implemented with Array or LinkedList
• store index
• use stack to implement queue, two stack swap reference, push O(n), pop O(1), peek O(1)