1. Standard Template Library
The STL is a large part of the C++ Standard Library
Major components
data structures (containers/collections for data – CS2851)
vector (array), list, deque, stack, queue, set, …
algorithms
Common operations (functions) that can be applied to many STL containers
iterators
link the algorithms to the data structures.
iterators are designed for efficient traversal through the data structures.
Similar to pointers
Fall 2005
CS-1030 Dr. Mark L. Hornick

2. Linked Lists – the list class
Arranges data in non-contiguous blocks
Links them together to create order
Stored Object
Link to Previous Cell
Link to Next Cell
Fall 2005
CS-1030 Dr. Mark L. Hornick

3. list is a Doubly Linked List
Last
First
Size
Main List Cell
Data
Data …
Data …
Fall 2005
CS-1030 Dr. Mark L. Hornick

4. list in C++ (STL) Syntax #include <list> using namespace std;
list<T> collection;
// T: datatype stored in vector
Fall 2005
CS-1030 Dr. Mark L. Hornick

5. list Operations Adding elements Removing an element
push_back – At the end
push_front – At the beginning
insert – Anywhere
Removing an element
pop_back – From the end
pop_front – From the beginning
erase, remove - Anywhere
Fall 2005
CS-1030 Dr. Mark L. Hornick

6. list Operations (2) Information accessors/inspectors Modification
size – How many?
empty – Are there none?
Modification
sort – NOT part of <algorithm>
reverse – change the order
Fall 2005
CS-1030 Dr. Mark L. Hornick

7. The vector class vector is a “smart” array Like the Java ArrayList
Storage is in consecutive memory locations
Location =
start + index*size
Very little storage overhead
Only need the start and object size 1 …
n-1
vector start 
Fall 2005
CS-1030 Dr. Mark L. Hornick

8. vectors in C++ (STL) User-specified data type is stored Syntax:
#include <vector>
using namespace std;
vector<T> collection;
// T: datatype stored in vector
// Like Java’s ArrayList<T>
Fall 2005
CS-1030 Dr. Mark L. Hornick

9. vector Operations Adding elements: Removing an element
push_back – At the end
push_front – At the beginning
insert – Anywhere
Removing an element
pop_back – From the end
pop_front – From the beginning
erase, remove - Anywhere
Fall 2005
CS-1030 Dr. Mark L. Hornick

10. lists and vectors usage
Example
Fall 2005
CS-1030 Dr. Mark L. Hornick

11. lists vs. vectors Advantages Disadvantages Flexible storage
Grows easier
Ultimately more data can be stored
Disadvantages
O(n) access time
Loss of indexing
Storage overhead is higher
Fall 2005
CS-1030 Dr. Mark L. Hornick

12. Iterators A mechanism for sequentially accessing
STL containers
More important for list than vector
Vector can use indexing for access (e.g. x[i])
Automatically included as part of the container
Helps describe the next and previous links
Fall 2005
CS-1030 Dr. Mark L. Hornick

13. Iterator Notation Declaration Operators
list<TYPE>::iterator NAME;
Operators
* Access data element (dereferencing)
++,-- Advance or retreat in the list
==,!= Comparison
NOTE: No < or >
Fall 2005
CS-1030 Dr. Mark L. Hornick

14. Iterators in a Linked List
Main List Cell
.begin()
Size
First
Last
Data
Data … …
Data …
.end()
Fall 2005
CS-1030 Dr. Mark L. Hornick

15. Iterator Variations Standard iterators can be used to change a list
*iter = newValue;
Special iterators for const lists (can’t change)
list<TYPE>::const_iterator citer;
Reverse iterators
list<TYPE>::reverse_iterator riter;
list<TYPE>::const_reverse_iterator
criter;
Fall 2005
CS-1030 Dr. Mark L. Hornick

16. More on Reverse Iterators
For going from end to beginning
++ Retreats
-- Advances
Bounds
rbegin() – Last
rend() – One “before” the first
Fall 2005
CS-1030 Dr. Mark L. Hornick

17. Other iterator Member Functions
These member functions need iterators
insert – Where to insert
erase – Which one to erase
find – Locate the item that was found
Iterators also apply to vectors
Usage is the same
vector<TYPE>::iterator NAME;
Fall 2005
CS-1030 Dr. Mark L. Hornick

18. STL Algorithms
An algorithm is an operation (function) that can be applied to many STL containers
The STL algorithms are generic - they can operate on a variety of data structures.
STL container classes such as vector and list
Program-defined data structures
Behavior must satisfy the requirements of a particular algorithm
STL algorithms achieve generality by accessing and traversing the elements of a container indirectly through iterators.
Iterators must be settable and dereferencable
Fall 2005
CS-1030 Dr. Mark L. Hornick

19. Sort Algorithm
The sort algorithm is an operation (function) that can be applied to many STL containers
notable exception: list container (has it’s own method)
sort() orders a container's contents in ascending order
as defined by the operator<() as applied to the container’s elements
Programmer-defined types can be sorted just as easily as a built-in type
Fall 2005
CS-1030 Dr. Mark L. Hornick

20. find Algorithm
searches a subrange of the elements in a container (or all the elements),
looks for an element that is "equal to" a specified value; stops when it finds the first element equal to the specified value
the equality operator (==) must be defined for the type of the container's elements.
search value must be of the same type as the elements stored in the container
or of a type that the compiler can automatically convert.
Return value is an iterator specifying the position of the first matching element.
If no matching element is found, the return value is equal to the iterator specifying the end of the element subrange
Fall 2005
CS-1030 Dr. Mark L. Hornick