NETB201 Data Structures

Chapter 1: Basic C++ Programming

1.1 Basic C++ Programming Elements

1.1.1 A Simple C++ Program

#include <stdlib>
#include <iostream>
int main()
{ int x, y;
  std::cout << "Please enter two numbers: "; 
  std::cin >> x >> y;       // input stream 
  int sum = x + y;
  std::cout << "Their sum is " << sum << std::endl;
  return EXIT_SUCCESS;
}

Highlighting the C++ Elements

• header files
• function body
• standard output stream std::cout
• standard input stream std::cin
• standard error stream std::cerr
• using namespace std;

1.1.2 Fundamental Types

Characters

cout << 'a' << int('a') << static_cast<int>('a');

Integers

• long constant: 123456789L
  
• octal (base 8) integer constant (using digits 0,1,2,3,4,5,6,7): 0273
  
• hexadecimal (base 16) integer constant (using digits 0,..9, A, B, C, D, E, F): 0xA05
  

Enumerations

enum Color { RED, GREEN, BLUE };  // default values are 0, 1, 2
enum Week { MONDAY = 1, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY};  
                                  // values are 1, 2, 3, .., 7
enum Mood { HAPPY = 3, SAD = 1, ANXIOUS = 4, SLEEPY = 2 };
Color skyColor = BLUE;
Mood myMood = SLEEPY;
Week day = TUESDAY;

Floating Point

1.1.3 Pointers, Arrays, and Structures

Pointers

char ch = 'Q';  
char* p = &ch;   // p holds the address of ch 
cout << *p;      // outputs the character 'Q'    
ch = 'Z';        // ch now holds 'Z'  
cout << *p;      // outputs the character 'Z'  

Arrays

double f[3];    // array of 3 doubles f[0], f[1], f[2]
double* p[10];  // array of 10 double pointers p[0]..p[9]
f[2] = 2.5;
p[4] = &f[2];   // p[4] points to f[2]
cout << *p[4];  // outputs 2.5
int a[] = { 10, 11, 12, 13 }; // initialization
int b[20] = { 0 }; // initialize all elements with value 0

Pointers and Arrays

char ch[] = {'c', 'a', 't'};
char* p = c;             // p points to c[0]
char* q = &c[0];         // q also points to c[0]
cout << c[2] << p[2] << q[2];  // outputs "ttt"

Strings

#include<string>;
using std::string;
//...
  string s = "to be";
  string t = "not " + s;     // t := "not to be"
  string u = s + " or " + t; // u := "to be or not to be"
  if (s > t) cout u;
//...
  s = "John";           
  int i = s.size();    // i = 4
  char c = s[3];       // c = 'n'
  s += " Smith";       // s = "John Smith"
  char *p = s.c_str(); // p is a C-style string

C-Style Structures

enum MealType { NO_PREF, REGULAR, LOW_FAT, VEGETARIAN };
struct Passenger {
    string name;         // "John Smith"
    MealType mealPref;   // LOW_FAT 
    bool isFreqFlyer;    // true
    string freqFlyerNo;  // "293145"
};

Passenger pass = { "John Smith", LOW_FAT, true, "293145" };
pass.name = "Pocahontas";    // change name
pass.mealPref = VEGETARIAN;  // change meal preference

Pointers, Dynamic Memory, and the new Operator

Passenger *p;
//...
p = new Passenger;         // p points the new Passenger
p->name = "Pocahontas";    // member selection(arrow) operator
p->mealPref = VEGETARIAN;  // change meal preference
p->isFreqFlyer = false;
p->freqFlyerNo = "NONE";
//...
delete p;

Memory Leaks

char* buffer = new char[500];
//...
delete buffer; // ERROR: delete only the fist element buffer[0] 

char* buffer = new char[500];
//...
delete [] buffer; // delete all elements 

1.1.4 Scope and Namespaces

Constants and typedef

const double PI = 3.14159265;
const int CUT_OFF[] = {90, 80, 70, 60};
const int N_DAYS = 7;
const int N_HOURS = 24*N_DAYS;
int counter[N_HOURS];

typedef char* BufferPtr;   // type BufferPtr is a pointer to char
typedef double Coordinate; // type Coordinate is a double
//...
BufferPtr p;       // p is a pointer to a char
Coordinate x, y;   // x and y are of type double

Local and Global Scopes

const int cat = 1;      // global cat
int main() 
{  const int cat = 2;   // local cat (to main)
   cout << cat;         // outputs 2
   return 0;
}
int dog = cat;          // dog = 1 (from global cat)

Namespaces

namespace myglobals {
   int cat; 
   string dog = "bow wow";
}
   
int d = myglobals::cat;

The Using Statement

using std::cout;
using myglobals::cat;

using namespace std;
using namespace myglobals;

1.2 Expressions

• var to denote a variable or anything to which a value may be assigned (lvalue);
• exp to denote an expression (rvalue);
• T to denote a type.

Member Selection and Indexing

• class_name denote the name of a structure or class;
• member denote a member (or field) of this structure or class;
• pointer denote a pointer to a structure or class;
• array denote an array or a pointer to the first element of an array.

Increment and Decrement Operators

int a[] = { 0, 1, 2, 3 };
int i = 2;           
int j = i++;         // j = 2 and then i = 3
int k = --i;         // i = 2 and k = 2
cout << a[k++];      // a[2] (=2) is output; now k = 3

Relational and Logical Operators

Bitwise Operators

Arithmetic operators (+, -, *,  /, % ) and bitwise binary operators (&, ^, |, <<, >>) combine with assignment.

int i = 10; 
int j = 5;
int k = 1;
i -= 4;     // i = i - 4; result 6
j *= -2;    // j = j * (-2); result -10
k <<= 1;    // k = k << 1; result 2

Other Operators

int a = 10, b, c, d;  
// right associativity  
d = c = b = a;     // is equivalent to d = (c = (b = a)); 
// left associativity  
d - c + b - a;     // is equivalent to ((d - c) + b) - a;    
d > c && -b <= a   // is equivalent to (d>c) && ((-b)<=a)  

1.2.1 Casting in Expressions

Traditional C-Style Casting

• (T)exp - C-style cast
• exp(T) - functional-style cast

int cat = 14;  
double dog = (double)cat; 
double pig = double(cat);

Explicit Cast Operators

• short to int - harmless
• double to int - dangerous (the fractional part of the number is lost)
• double* to char* - dangerous (depends of the compiler, OS, hardware)

The standard of C++ supports 4 casting versions (operators):

• static_cast
• dynamic_cast
• const_cast
• reinterpret_cast

using the notation: some_cast<T>(exp).

Static Casting

static_cast<T>(exp)

int cat = 14;  
double dog = static_cast<double>(cat); // dog := 14.0 
double lion = 155.99;
int pig = static_cast<int>(lion);      // pig := 155

Implicit Casting

implicit_cast.cpp

1.3 Control Flow

1.4 Functions

1.4.1 Argument Passing

 1.4.2 Overloading

Function Overloading

void print(int x)
{ cout << x; } 
void print(const Passenger &pass)
{ cout << pass.name << " " << pass.mealPref;
  if (pass.isFreqFlyer) cout << pass.freqFlyerNo;
}

bool operator==(const Passenger &x, const Passenger &y)
{ return x.name == y.name &&
         x.mealPref == y.mealPref &&
         x.isFreqFlyer == y.isFreqFlyer &&
         x.freqFlyerNo == y.freqFlyerNo;
}

Using Overloading

ostream& operator<<(ostream &out, const Passenger &pass)
{ out << pass.name << " " << pass.mealPref;
  if (pass.isFreqFlyer) out << pass.freqFlyerNo;
  return out;
}
//...
Passenger pass1 = // details omitted
Passenger pass2 = // details omitted
cout << pass1 << pass2 << endl;

1.5 Classes

1.5.1 Class Structure

Access Control

Member Functions

enum MealType { NO_PREF, REGULAR, LOW_FAT, VEGETARIAN };
class Passenger {
  private:
    string name;         // "John Smith"
    MealType mealPref;   // LOW_FAT 
    bool isFreqFlyer;    // true
    string freqFlyerNo;  // "293145"
  public:
    Passenger();                 // default constructor
    bool isFreqFlyer() const;    // accessor function                                         
    void makeFreqFlyer(const string &newFreqFlyerNo);
                                 // update (mutator) function   
};
// ...
bool Passenger::isFreqFlyer() const
{ return isFreqFlyer; }
void Passenger::makeFreqFlyer(const string &newFreqFlyerNo)
{ isFreqFlyer = true;
  freqFlyerNo = newFreqFlyerNo;
}
//...
Passenger pass;
//...
if (!pass.isFreqFlyer())          // OK
   pass.makeFreqFlyer("999999");  // OK
pass.name = "Joe Blow";           // ERROR: private member

In-Class Function Definition

enum MealType { NO_PREF, REGULAR, LOW_FAT, VEGETARIAN };
class Passenger {
  private:
    string name;         // "John Smith"
    MealType mealPref;   // LOW_FAT 
    bool isFreqFlyer;    // true
    string freqFlyerNo;  // "293145"
  public:
    Passenger();
    bool isFreqFlyer() const
    { return isFreqFlyer; }     
    void makeFreqFlyer(const string &newFreqFlyerNo)
    { isFreqFlyer = true;
      freqFlyerNo = newFreqFlyerNo;
    }
};

1.5.2 Constructors and Destructors

1.5.3 Classes and Memory Allocation

1.5.4 Class Friends and Class Members

class Matrix;              // Matrix definition comes later
class Vector {             // a 3-element vector
private:
  double coord[3];
public:
  // ...
  friend class Matrix;     // allow Matrix access to coord
};
class Matrix {             // a 3x3 array
private:
  double a[3][3];
public:
  // ...
  Vector multiplyBy(const Vector& v) {  // multiply (a * v)
    Vector w(0, 0, 0);
    for (int i = 0; i < 3; i++)
      for (int j = 0; j < 3; j++)
        w.coord[i] += a[i][j] * v.coord[j]; // access private data
    return w;
  }
};

Nesting Classes and Types within Classes

class Complex {
private:
    class Node {
    // ... 
    };
    //... 
};

1.5.5 The Standard Template Library

Templates and the STL Vector Class

vector<int> scores(100);  
vector<char> buffer(500); 
vector<Passenger> passList(20);
vector<int> newScores = scores;