CS 13012 Computer Science IB: Object Oriented Programming Final Exam 2

Structures Structure declaration Structure variable declaration struct CDAacct{ int balance; int rate; int term; }; Structure variable declaration CDAcct myacct, youracct; How to access members (or member variables) of the structure variable? myacct.balance

Structures (cont'd) Initialization of structure variable CDAcct myacct={1000, 9, 12}; Assignment of structure variables CDAcct youracct; youracct=myacct; Structure variables cannot be directly compared if (youracct == myacct) // error Structure can be used as parameters of a function (passing by reference or by value) and can be also returned from the function Complex structures Members of a structure can be other structures or arrays

Classes Class definition Object class Date { // class name public: // ignore this for now void set(int, int, int); int getDay(); int month; int day; int year; }; // don’t forget the semicolon Member variables Member functions Access control: public, private Object Date mybday; Each object belongs to a class; each class can have multiple objects (instances)

Classes (cont'd) Access member variables/functions in the object mybday.set(10, 26, 68); cout << mybday.day; Member function declaration In-line definition Out-of-line definition void Date::set(int m, int d, int y){...} Mutator vs. accessor class Date { public: // mutator void set(int, int, int); // mutator int getMonth() const; // accessor int getDay() const {return day;} // accessor in-line private: int month; int day; int year; };

Classes (cont'd) Classes with objects Constructors Destructors Member variables can be objects of other classes Constructors void or default constructor Date(); // constructor in class Date Normal constructor Date(int, int, int); // constructor in class Date Copy constructor Date(const Date &); Destructors ~Date(); Initializer list Date(int m, int d, int y): month(m), day(d), year(y) {}

Pointers Pointer declaration Pointer initialization Use the pointer int *p; Pointer initialization int i; int *p = & i; Assign an array to a pointer: int arr[3]; p=arr; Use the pointer *p= 1; cout << *p<<endl;

Pointers (cont'd) Pointer arithmetic int a[5], *p = a; p = p + 1; p = p – 1; p++; p+=2; Null pointer or loose pointer problem int *ptr; *ptr = 5; // ERROR - loose pointer! Memory leak problem int *ptr = new int[3]; int *ptr2 = new int[10]; ptr = ptr2;

Dynamic Memory Allocation new – allocate memory space int *ip; // declares pointer ip = new int; // ip points to integer variable int *ip2 = new int(5); // 5 assigned to the var int *ip3 = new int[10]; // allocate an array of size 5 Myclass * obj = new Myclass; // dynamically create an object delete – deallocate memory space delete ip; delete ip2; delete [] ip3; Memory leak problem (see previous slide) Pointers can be passed into the function by reference or by value, and be returned from a function

Dynamic Memory Allocation (cont'd) Dynamic objects myclass *mp1; mp1 = new myclass(5); Access member variables/functions for an object pointer cout << mp1->getdata(); (*mp1).getdata();

Objects Containing Dynamically Allocated Members Dynamically allocate an array within an object class MyClass{ public: MyClass(int); // constructor ~MyClass(); // destructor MyClass(const MyClass&); // copy constructor private: int *d; int size; }; // constructor MyClass::MyClass(int n){ size=n; d = new int[size]; }

Objects Containing Dynamically Allocated Members (cont'd) Destructor MyClass::~MyClass(){ delete [] d; } Copy constructor Pass an object into a function by value Return an object by a function MyClass::MyClass(const MyClass& org){ size=org.size; d = new int[size]; for(int i=0; i< size; ++i) d[i]=org.d[i];

Vectors Vector vs array Vector declaration Vector operations Why vector? Vector declaration vector<int> items; // declares vector with no elements vector<double> items(5); // declares vector with 5 elements vector<myclass> items(5); // declares a vector of 5 objects of myclass Vector operations items [3];

Vectors (cont'd) Vector functions return the vector size: items.size(); adding element: items.push_back(55); removing element: items.pop_back(); emptying: items.erase(); Deleting specific location: items.erase(item_iterator);

Vectors (cont'd) Iterators The usage of vector iterators vector<typeParameter>::iterator iteratorName; e.g., vector<int>::iterator ip; v.begin() returns an iterator pointing to the first element of container v v.end() returns an iterator pointing past the last element of container v useful to compare for end of iteration Insert: v.insert(ip, 22); // inserts one element at // iterator ip position v.insert(v.end()-2, 55); // ? Delete: v.erase(ip); // erases one element at // iterator ip position The usage of vector iterators

Multidimensional Arrays, Vectors of Vectors Multidimensional array declaration int a[3][4]; How to access or iterate over elements in the multidimensional array? Nested for loop Vector of vectors How to create and initialize a vector of vectors? vector<vector<int>> a; vector<int> row(width); for(int i=0; i < length; ++i) a.push_back(row);

Multidimensional Arrays, Vectors of Vectors (cont'd) Ragged array Rows can be of different sizes vector<int> row; vector<vector<int>> a; for(int i=0; i < 4; ++i){ row.push_back(i); a.push_back(row); } See the code on vector of vectors, iterators, and ragged array in lecture slides

Namespaces Name collision problem Three different styles of using namespaces std is one of examples std::cout<<"hello"<<std::endl; using std::cout; using std::endl; // at the beginning of the program using namespace std; // at the beginning of the program

Recursion A function calls itself Examples Attention: base case Function write_vertical() in the lecture slides Function of computing factorial of n (i.e., n!) Attention: base case