# C++ Programming Code Examples

## C++ > Data Structures and Algorithm Analysis in C++ Code Examples

### Polynomials

/* Polynomials */ /* * This code doesn't really do much, and abstraction is not built in. * Thus, I haven't bothered testing it exhaustively. */ #include <iostream.h> #include "vector.h" class Polynomial { enum { MAX_DEGREE = 100 }; friend int main( ); // So I can do a quick test. public: Polynomial( ); void zeroPolynomial( ); Polynomial operator+( const Polynomial & rhs ) const; Polynomial operator*( const Polynomial & rhs ) const; void print( ostream & out ) const; private: vector<int> coeffArray; int highPower; }; int max( int a, int b ) { return a > b ? a : b; } Polynomial::Polynomial( ) : coeffArray( MAX_DEGREE + 1 ) { zeroPolynomial( ); } void Polynomial::zeroPolynomial( ) { for( int i = 0; i <= MAX_DEGREE; i++ ) coeffArray[ i ] = 0; highPower = 0; } Polynomial Polynomial::operator+( const Polynomial & rhs ) const { Polynomial sum; sum.highPower = max( highPower, rhs.highPower ); for( int i = sum.highPower; i >= 0; i-- ) sum.coeffArray[ i ] = coeffArray[ i ] + rhs.coeffArray[ i ]; return sum; } Polynomial Polynomial::operator*( const Polynomial & rhs ) const { Polynomial product; product.highPower = highPower + rhs.highPower; if( product.highPower > MAX_DEGREE ) cerr << "operator* exceeded MAX_DEGREE" << endl; for( int i = 0; i <= highPower; i++ ) for( int j = 0; j <= rhs.highPower; j++ ) product.coeffArray[ i + j ] += coeffArray[ i ] * rhs.coeffArray[ j ]; return product; } void Polynomial::print( ostream & out ) const { for( int i = highPower; i > 0; i-- ) out << coeffArray[ i ] << "x^" << i << " + "; out << coeffArray[ 0 ] << endl; } ostream & operator<<( ostream & out, const Polynomial & rhs ) { rhs.print( out ); return out; } int main( ) { Polynomial p; Polynomial q; p.highPower = 1; p.coeffArray[ 0 ] = 1; p.coeffArray[ 1 ] = 1; q = p + p; p = q * q; q = p + p; cout << q << endl; return 0; }

Standard output stream for errors. Object of class ostream that represents the standard error stream oriented to narrow characters (of type char). It corresponds to the C stream stderr. The standard error stream is a destination of characters determined by the environment. This destination may be shared by more than one standard object (such as cout or clog). As an object of class ostream, characters can be written to it either as formatted data using the insertion operator (operator<<) or as unformatted data, using member functions such as write. The object is declared in header <iostream> with external linkage and static duration: it lasts the entire duration of the program.

In computer programming, we use the if statement to run a block code only when a certain condition is met. An if statement can be followed by an optional else statement, which executes when the boolean expression is false. There are three forms of if...else statements in C++: • if statement, • if...else statement, • if...else if...else statement, The if statement evaluates the condition inside the parentheses ( ). If the condition evaluates to true, the code inside the body of if is executed. If the condition evaluates to false, the code inside the body of if is skipped.

An array is defined as the collection of similar type of data items stored at contiguous memory locations. Arrays are the derived data type in C++ programming language which can store the primitive type of data such as int, char, double, float, etc. It also has the capability to store the collection of derived data types, such as pointers, structure, etc. The array is the simplest data structure where each data element can be randomly accessed by using its index number. C++ array is beneficial if you have to store similar elements. For example, if we want to store the marks of a student in 6 subjects, then we don't need to define different variables for the marks in the different subject. Instead of that, we can define an array which can store the marks in each subject at the contiguous memory locations.

In computer programming, loops are used to repeat a block of code. For example, when you are displaying number from 1 to 100 you may want set the value of a variable to 1 and display it 100 times, increasing its value by 1 on each loop iteration. When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop. A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.

A friend function of a class is defined outside that class' scope but it has the right to access all private and protected members of the class. Even though the prototypes for friend functions appear in the class definition, friends are not member functions. A friend can be a function, function template, or member function, or a class or class template, in which case the entire class and all of its members are friends. If a function is defined as a friend function in C++ programming language, then the protected and private data of a class can be accessed using the function. By using the keyword friend compiler knows the given function is a friend function. For accessing the data, the declaration of a friend function should be done inside the body of a class starting with the keyword friend.

C supports nesting of loops in C. Nesting of loops is the feature in C that allows the looping of statements inside another loop. Any number of loops can be defined inside another loop, i.e., there is no restriction for defining any number of loops. The nesting level can be defined at n times. You can define any type of loop inside another loop; for example, you can define 'while' loop inside a 'for' loop. A loop inside another loop is called a nested loop. The depth of nested loop depends on the complexity of a problem. We can have any number of nested loops as required. Consider a nested loop where the outer loop runs n times and consists of another loop inside it. The inner loop runs m times. Then, the total number of times the inner loop runs during the program execution is n*m.

In C++, constructor is a special method which is invoked automatically at the time of object creation. It is used to initialize the data members of new object generally. The constructor in C++ has the same name as class or structure. Constructors are special class functions which performs initialization of every object. The Compiler calls the Constructor whenever an object is created. Constructors initialize values to object members after storage is allocated to the object. Whereas, Destructor on the other hand is used to destroy the class object. • Default Constructor: A constructor which has no argument is known as default constructor. It is invoked at the time of creating object.

Access element. Returns a reference to the element at position n in the vector container. A similar member function, vector::at, has the same behavior as this operator function, except that vector::at is bound-checked and signals if the requested position is out of range by throwing an out_of_range exception. Portable programs should never call this function with an argument n that is out of range, since this causes undefined behavior. Function returns the element at the specified position in the vector.

A program shall contain a global function named main, which is the designated start of the program in hosted environment. main() function is the entry point of any C++ program. It is the point at which execution of program is started. When a C++ program is executed, the execution control goes directly to the main() function. Every C++ program have a main() function.

As the name already suggests, these operators help in assigning values to variables. These operators help us in allocating a particular value to the operands. The main simple assignment operator is '='. We have to be sure that both the left and right sides of the operator must have the same data type. We have different levels of operators. Assignment operators are used to assign the value, variable and function to another variable. Assignment operators in C are some of the C Programming Operator, which are useful to assign the values to the declared variables. Let's discuss the various types of the assignment operators such as =, +=, -=, /=, *= and %=. The following table lists the assignment operators supported by the C language:

In C++, vectors are used to store elements of similar data types. However, unlike arrays, the size of a vector can grow dynamically. That is, we can change the size of the vector during the execution of a program as per our requirements. Vectors are part of the C++ Standard Template Library. To use vectors, we need to include the vector header file in our program. The vector class provides various methods to perform different operations on vectors. Add Elements to a Vector: To add a single element into a vector, we use the push_back() function. It inserts an element into the end of the vector. Access Elements of a Vector: In C++, we use the index number to access the vector elements. Here, we use the at() function to access the element from the specified index.

Abstraction is one of the feature of Object Oriented Programming, where you show only relevant details to the user and hide irrelevant details. For example, when you send an email to someone you just click send and you get the success message, what actually happens when you click send, how data is transmitted over network to the recipient is hidden from you (because it is irrelevant to you). • Data Abstraction is a process of providing only the essential details to the outside world and hiding the internal details, i.e., representing only the essential details in the program. • Data Abstraction is a programming technique that depends on the seperation of the interface and implementation details of the program. • Let's take a real life exa

Enumeration is a user defined datatype in C/C++ language. It is used to assign names to the integral constants which makes a program easy to read and maintain. The keyword "enum" is used to declare an enumeration. It can be used for days of the week (SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY and SATURDAY) , directions (NORTH, SOUTH, EAST and WEST) etc. The C++ enum constants are static and final implicitly. C++ Enums can be thought of as classes that have fixed set of constants.

The main purpose of C++ programming is to add object orientation to the C programming language and classes are the central feature of C++ that supports object-oriented programming and are often called user-defined types. A class is used to specify the form of an object and it combines data representation and methods for manipulating that data into one neat package. The data and functions within a class are called members of the class.

#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program.