Data Structures Using C++ 2E Chapter 4 Standard Template Library (STL) I 1

Objectives Learn about the Standard Template Library (STL) Become familiar with the three basic components of the STL: containers, iterators, and algorithms (in Chapter 13) Explore how vector and deque containers are used to manipulate data in a program Discover the use of iterators Data Structures Using C++ 2E

Different C++/STL versions C++11 is the ISO C++ standard ratified in 2011. The previous standard is often referred to as C++98/C++03; the differences between C++98 and C++03 are very few. The list of STL classes in both C++ and C++98 can be found under http://www.cplusplus.com/reference/stl/ This materials of this textbook is based on C++ 98 Data Structures Using C++ 2E

Components of the STL Program’s main objective is to manipulate data and generate results Requires ability to store data, access data, and manipulate data STL components Containers Iterators: step through container elements Algorithms: manipulate data (e.g. sorting, search) Containers and iterators Class templates (types as class arguments) Data Structures Using C++ 2E

Container Types STL containers categories Sequence containers (sequential containers) Associative containers Container adapters Data Structures Using C++ 2E

Container Types STL containers categories Sequence containers (sequential containers) vector, deque, list… Associative containers set, map, multiset, multimap… Container adapters: adaptation of sequence or associative class containers by modifying and restricting its interface for some special purpose. stack (LIFO), queue (FIFO), priority_queue… Data Structures Using C++ 2E

Containers, Associated Header Files, and Iterator Support

STL containers From http://cs.brown.edu/~jak/proglang/cpp/stltut/tut.html

STL: Sequence containers Contiguous blocks of objects; elements can be inserted at any point in the sequence; sequences are indexed by integers Vector Fast insertion at end, and allow random access. List Fast insertion anywhere, but provide only sequential access. Deque Fast insertion at either end, and allow random access. Data Structures Using C++ 2E

STL: Associative containers Associative containers are a generalization of sequences; can be indexed by any type (e.g., an ID or a name) Implemented with a data structure called binary search tree, which will be covered later in this course. Data Structures Using C++ 2E

STL: Associative containers Sets: add, delete, search, and iterate through the set. Multisets: Multisets are just like sets, except that duplicate copies of the same element are allowed. Maps: Maps represent a mapping from one type (the key type) to another type (the value type). You can associate a value with a key, or find the value associated with a key, very efficiently; you can also iterate through all the keys. Multimaps: are just like maps except that there is no limit on elemenets with the same key. Data Structures Using C++ 2E

Sequence Containers Every object has a specific position Predefined sequence containers vector , deque , list Sequence container vector Logically: same as arrays Processed like arrays All containers Use same names (e.g. push_back()) for common operations May have specific operations Data Structures Using C++ 2E

Arrays Static arrays int foo[100]; Dynamic arrays Data Structures Using C++ 2E

Sequence Container: vector Vector container Stores, manages objects in a dynamic array Elements accessed randomly Time-consuming item insertion: middle, beginning Fast item insertion: end Class implementing vector container vector Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) Using a vector container in a program requires the following statement: #include <vector> Defining a vector container object Specify object type Example: vector<int> intlist; Example: vector<string> stringList; Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) Declaring vector objects TABLE 4-1 Various ways to declare and initialize a vector container

Declare and initialize a vector Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) Manipulating data stored in a vector sequence container Basic operations Item insertion Item deletion Stepping through the elements of a vector array Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) Difference: .at (index) checks if index is out of bound, while [index] doesn’t. Data Structures Using C++ 2E

Access a vector Data Structures Using C++ 2E

vector: size vs. capacity Size: the number of elements you have used. Capacity: allocated space. In STL, it’s doubled each time if additional space is needed. “double the size” is out of a careful design. Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) Function push_back Adds element to end of container Used when declaring vector container Specific size unknown Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) class vector provides various operations to process vector container elements Iterator The argument position in STL terminology Data Structures Using C++ 2E

Iterators Iterators provide a way of specifying a position in a container. The code vector<int> v; // add some integers to v vector::iterator i1 = v.begin(); vector::iterator i2 = v.end(); will create two iterators like this: Note: v.end() actually returns the past-the-end position Data Structures Using C++ 2E

Declaring an Iterator to a Vector Container Even though we can process vector like an array using array [ ] operator, sometimes we need to process vector elements based on their positions. class vector: function insert Insert element at a specific vector container position Uses an iterator class vector: function erase Remove element Data Structures Using C++ 2E

Declaring an Iterator to a Vector Container (cont’d.) class vector contains iterator (a typedef inside the class vector), declared as a public member of vector https://www.sgi.com/tech/stl/stl_vector.h typedef value_type* iterator; (nothing but a pointer!) If you want to declare a vector iterator, you’d need to use the scope resolution operator :: to specify which type of vector the iterator belongs to. Example vector<int>::iterator intVecIter; Data Structures Using C++ 2E

Declaring an Iterator to a Vector Container (cont’d.) vector<int>::iterator intVecIter; Container name (vector) Container data type (int) Scope resolution operator (::) ++intVecIter Advances iterator intVecIter to next element into the container *intVecIter Returns element at current iterator position Data Structures Using C++ 2E

Manipulation we can do with iteartors Using an iterator into a vector container Manipulating element type to be int Data Structures Using C++ 2E

Containers and the Functions begin and end Returns position of the first element into the container end() Returns position of (past) the last element into the container Functions have no parameters Data Structures Using C++ 2E

Example 4-4 Data Structures Using C++ 2E

Sequence Container: vector (cont’d.) TABLE 4-3 Various operations on a vector container Data Structures Using C++ 2E

Vector: other functions TABLE 4-3 Various operations on a vector container (cont’d.) http://www.cplusplus.com/reference/vector/vector/vector/ http://www.cplusplus.com/reference/vector/vector/resize/ Data Structures Using C++ 2E

Containers and the Functions begin and end (cont’d.) TABLE 4-4 Functions to determine the size of a vector container Data Structures Using C++ 2E

More examples of STL vector http://www.cplusplus.com/reference/stl/ http://www.cplusplus.com/reference/vector/vector/ https://www.sgi.com/tech/stl/Vector.html Data Structures Using C++ 2E

Member Functions Common to All Containers Constructors & destructor Default constructor, Several constructors with parameters, Copy constructor, Destructor Container operations: insert(), erase(), begin(), end(), etc… Containers operations: Assignment Comparison: equal to or not, >, < ,… Lexicographic order, for the entire container.

TABLE 4-5 Member functions common to all containers http://www.cplusplus.com/reference/vector/vector/max_size/ Data Structures Using C++ 2E

Member Functions Common to Sequence Containers TABLE 4-6 Member functions common to all sequence containers http://www.cplusplus.com/reference/vector/vector/insert/ Data Structures Using C++ 2E

The copy Algorithm Provides convenient way to output container elements Generic STL algorithm Usable with any container type and arrays Does more than output container elements Allows copying of elements from one place to another Function template copy definition Contained in header file algorithm Data Structures Using C++ 2E

copy examples http://www.cplusplus.com/reference/algorithm/copy/

Sequence Container: deque Deque: double-ended queue Implemented as dynamic arrays Can expand in either direction Class name defining deque container deque Header file deque contains Definition of the class deque Functions to implement various operations on a deque object Class deque contains several constructors http://www.cplusplus.com/reference/deque/deque/ https://www.sgi.com/tech/stl/Deque.html Data Structures Using C++ 2E

Sequence Container: deque (cont’d.) TABLE 4-7 Various ways to declare a deque object Data Structures Using C++ 2E

Sequence Container: deque (cont’d.) TABLE 4-8 Various operations that can be performed on a deque object Data Structures Using C++ 2E

More examples about STL deque http://www.cplusplus.com/reference/deque/deque/ https://www.sgi.com/tech/stl/Deque.html Data Structures Using C++ 2E

STL: Iterators in general Work like pointers Point to elements of a container (sequence or associative) Allow successive access to each container element Two most common operations on iterators ++ (increment operator) * (dereferencing operator) Examples ++cntItr; *cntItr; http://en.wikipedia.org/wiki/Increment_and_decrement_operators Data Structures Using C++ 2E

Types of Iterators Input iterators Output iterators Forward iterators Bidirectional iterators Random access iterators Data Structures Using C++ 2E

Operations supported by the iterators Read access; step forward int t = *inputIter; ++inputIter; write access; step forward *outputIter = t; ++outputIter; Both read/write; step forward Both read/write; step forward and backward. Supported in list, set, map, multiset, multimap Both read/write; jump forward and backward. rIterator = rIterator + n; Supported in vector deque, string, array

Input Iterators Read access Step forward element-by-element Return values element-by-element Provided for reading data from an input stream Data Structures Using C++ 2E

Input Iterators (cont’d.) TABLE 4-9 Operations on an input iterator Data Structures Using C++ 2E

Output Iterators Write access Step forward element-by-element Used for writing data to an output stream Cannot be used to iterate over a range twice Data Structures Using C++ 2E

Output Iterators (cont’d.) TABLE 4-10 Operations on an output iterator Data Structures Using C++ 2E

Forward Iterators Combination of All of input iterators functionality and almost all output iterators functionality Can refer to same element in same collection Can process same element more than once Data Structures Using C++ 2E

Forward Iterators (cont’d.) TABLE 4-11 Operations on a forward iterator Data Structures Using C++ 2E

Bidirectional Iterators Forward iterators that can also iterate backward over the elements Operations defined for forward iterators applicable to bidirectional Iterators To step backward Decrement operations also defined for biDirectionalIterator Can be used only with containers of type: vector, deque, list, set, multiset, map, and multimap Data Structures Using C++ 2E

Bidirectional Iterators (cont’d.) TABLE 4-12 Additional operations on a bidirectional iterator Data Structures Using C++ 2E

Random Access Iterators Bidirectional iterators that can randomly process container elements Can be used with containers of type: vector , deque , string, and arrays Operations defined for bidirectional iterators applicable to random access iterators Data Structures Using C++ 2E

Random Access Iterators (cont’d.) TABLE 4-13 Additional operations on a random access iterator Data Structures Using C++ 2E

Iterators (cont’d.) typedef iterator Every container (sequence or associative) contains a typedef iterator Iterator into a container declared using typedef iterator. For example Must use appropriate container name, container element type, scope resolution operator Data Structures Using C++ 2E

Iterators (cont’d.) typedef const_iterator Modify container elements using an iterator into a container and dereferencing operator (*) Prevents iterator from modifying elements of container declared as constant Every container contains typedef const_iterator Read-only iterator Data Structures Using C++ 2E

Iterators (cont’d.) typedef reverse_iterator Every container contains typedef reverse_iterator Used to iterate through the elements of a container in reverse Data Structures Using C++ 2E

Iterators (cont’d.) typedef const_reverse iterator Read-only iterator Used to iterate through elements of a container in reverse Required if Container declared as const Need to iterate through the elements of the container in reverse Data Structures Using C++ 2E

Summary STL Iterators Algorithms Provides class templates Process lists, stacks, and queues Three main components Containers, iterators, and algorithms STL containers: class templates Iterators Step through the elements of a container Algorithms Manipulate elements in a container Data Structures Using C++ 2E

Summary (cont’d.) Main categories of containers Sequence containers, associative containers, container adapters Three predefined sequence containers vector, deque, and list copy algorithm Copies elements in a given range to another place Five categories of iterators: input, output, forward, bidirectional, random access iterator Data Structures Using C++ 2E