4)Abstract data types Examples include: A queue is a first-in first-out list.Variations are Deque and Priority queue. .A set can store certain values,without any particular order,and with no repeated values. A stack is a last-in,first out data structure. .A tree is a hierarchical structure. ·A graph. .A hash,dictionary,map or associative array is a more flexible variation on a record,in which name-value pairs can be added and deleted freely. .A smart pointer is the abstract counterpart to a pointer.Both are kinds of references. 16 DATA Copyright 2019 by Xiaoyu Li.Copyright © 2019 by Xiaoyu Li. 16 4）Abstract data types