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

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

3. 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

4. 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)

5. 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; };

6. 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) {}

7. 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;

8. 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;

9. 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

10. 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();

11. 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]; }

12. 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];

13. 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];

14. 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);

15. 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

16. 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);

17. 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

18. 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

19. 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