Vectors. CIS 15 : Spring 2007

Transcription

1 Vectors CIS 15 : Spring 2007

2 Functionalia Midterm 2 : Ave. 58% (36.9 / 68) Med. 67% (45.5 / 68) Today: Standard Template Library Vector Template

3 Standard Template Library C++ offers extended functionality than just the runtime library through the Standard Template Library. Basically, rather than re-invent the wheel on commonly written code (i.e. Linked Lists), the STL provides standard functionality through templates.

4 Templates Templates - imagine you can create Classes and Functions where the data type is abstracted and is generic. int addint(int a, int b) { return a + b; } double adddouble(double a, double b) { return a + b; }

5 Templates Templates - imagine you can create Classes and Functions where the data type is abstracted and is generic. int addint(int a, int b) { } return a + b; Same Algorithm double adddouble(double a, double b) { } return a + b;

6 What s in the STL? STL Data Structures

7 What s in the STL? STL Data Structures containers iterators

8 What s in the STL? STL Data Structures containers iterators sequence associative

9 What s in the STL? STL Data Structures containers iterators sequence associative vector deque list

10 What s in the STL? STL Data Structures containers iterators sequence associative vector deque list set multiset map multimap

11 What s in the STL? STL Data Structures containers iterators sequence vector deque list associative set multiset map multimap Forward Bidirectional Random-access Input Output

12 What s in the STL? STL Data Structures containers iterators sequence vector deque list associative set multiset map multimap Forward Bidirectional Random-access Input Output

13 Vectors Vectors are expandable arrays (dynamic in size). Values may be added to or removed from the end or middle of a vector. Like arrays: store values, and elements stored in contiguous memory locations can use the array [] notation to access members

14 Vectors Vectors are expandable arrays (dynamic in size). Values may be added to or removed from the end or middle of a vector. Like arrays: store values, and elements stored in contiguous memory locations can use the array [] notation to access members (and for backwards compatibility s sake).

15 Vectors Vectors are expandable arrays (dynamic in size). Values may be added to or removed from the end or middle of a vector. Unlike arrays: do not have to commit to a set size when declaring manages the size for you, increases it s size for you can report the size of it for you similar in functionality to the string class

16 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

17 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

18 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); vector is a template Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

19 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); declared to use the type int Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

20 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); numbers is the name of the vector Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

21 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

22 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

23 Defining a vector Use the vector STL library. #include <vector> Declares a vector object that can store integers. It is initially empty (size of 0) vector<int> numbers; Declares a vector that contains 10 integers. vector<int> numbers(10); Declares a vector that contains 10 integers all initialized to the value of 2. vector<int> numbers(10, 2); Copy one vector into another. vector<int> copy(numbers);

24 Using vectors vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) { numbers[i] = i; } Sets a list of numbers in ascending order.

25 Using vectors vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) { } numbers[i] = i; No need for array constant sizes, use the size() member function.

26 Using vectors vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) { numbers[i] = i; } Use the same array notation [].

27 Adding an element vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; numbers.push_back(11); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

28 Adding an element vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; numbers.push_back(11); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

29 Adding an element vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; numbers.push_back(11); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

30 Adding an element vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; Adds the element to the END of the vector numbers.push_back(11); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

31 Adding an element vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; numbers.push_back(11); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

32 Removing an element from the list vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; numbers.pop_back(); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

33 Removing an element from the list vector<int> numbers(10); for(int i = 0; i < numbers.size(); i++) numbers[i] = i+1; for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl; numbers.pop_back(); for(int i = 0; i < numbers.size(); i++) cout << numbers[i] << endl;

34 More Vector Member Functions vector<int> numbers(10); at(index) capacity() numbers.at(2); numbers.capacity(); Returns the value of the element at location index Returns the maximum number of elements in the vector currently clear() numbers.clear(); Clears the vector of all of its elements empty() reverse() resize(index, values) numbers.empty(); numbers.reverse(); numbers.resize(5,1); Returns true if the vector is empty, false otherwise Reverses the order of the elements in the vector Reinitializes the vector with index number of elements to value values swap(vector2) vector(int) numbers2(10); numbers.swap(numbers2); Swaps the members of the vector with that of vector2

35 More Vector Member Functions vector<int> numbers(10); at(index) capacity() numbers.at(2); numbers.capacity(); Returns the value of the element at location index Returns the maximum number of elements in the vector currently clear() numbers.clear(); Clears the vector of all of its elements empty() reverse() resize(index, values) numbers.empty(); numbers.reverse(); numbers.resize(5,1); Returns true if the vector is empty, false otherwise Reverses the order of the elements in the vector Reinitializes the vector with index number of elements to value values swap(vector2) vector(int) numbers2(10); numbers.swap(numbers2); Swaps the members of the vector with that of vector2

36 reverse error? error: 'class std::vector<int, std::allocator<int> >' has no member named 'reverse' No problem. The vector template has a reverse function available for you for use in this manner: vector<int> numbers; // using an int vector reverse(numbers.begin(), numbers.end());

37 reverse error? error: 'class std::vector<int, std::allocator<int> >' has no member named 'reverse' No problem. The vector template has a reverse function available for you for use in this manner: vector<int> numbers; // using an int vector reverse(numbers.begin(), numbers.end()); These member functions return iterators (used to access objects store in containers, an object-oriented index)

38 Using Vectors with Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } }; How would you create a vector of Dogs?

39 Using Vectors with Objects class Dog { string name; fido: woof! fido: woof! public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog> pack(10); Calls the Default Constructor. Then makes 9 more copies. pack[0].bark(); pack[1].bark();

40 Using Vectors with Dynamic Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog *> pack(10); Which constructor is called?

41 Using Vectors with Dynamic Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog *> pack(10); None of them. 10 Dog Pointers!

42 Using Vectors with Dynamic Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog *> pack; Not necessary to declare the vector size.

43 Using Vectors with Dynamic Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog *> pack; Add a Dog to the pack.

44 Using Vectors with Dynamic Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog *> pack; Default Constructor pack.push_back(new Dog); pack.push_back(new Dog( yo-yo ));

45 Using Vectors with Dynamic Objects class Dog { string name; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; } };... vector<dog *> pack; pack.push_back(new Dog); Other Constructor pack.push_back(new Dog( yo-yo ));

46 Write a loop to make all of the Dogs Bark! class Dog { string name; }; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; }... vector<dog *> pack; pack.push_back(new Dog); pack.push_back(new Dog( yo-yo ));

47 Use the size() member function. class Dog { string name; }; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; }... vector<dog *> pack; pack.push_back(new Dog); pack.push_back(new Dog( yo-yo )); for(int i = 0; i < pack.size(); i++) { } pack[i]->bark();

48 Clean up memory? class Dog { string name; }; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; }... vector<dog *> pack; pack.push_back(new Dog); pack.push_back(new Dog( yo-yo )); for(int i = 0; i < pack.size(); i++) { } pack[i]->bark();

49 Need to use delete on the Dog Pointers. class Dog { string name; }; public: Dog() { name = "fido"; } Dog(string n) { name = n; } void bark() { cout << name << ": woof!" << endl; }... vector<dog *> pack; pack.push_back(new Dog); pack.push_back(new Dog( yo-yo )); for(int i = 0; i < pack.size(); i++) { delete pack[i]; pack[i] = NULL; }

50 More Vector Member Functions Section 7.12 Section 16.5 Have more information about the vector template.