C++ Programming Code Examples
C++ > Data Structures and Algorithm Analysis in C++ Code Examples
Simple matrix class
/* Simple matrix class */
#ifndef MATRIX_H
#define MATRIX_H
#include "vector.h"
template <class Object>
class matrix
{
public:
matrix( int rows, int cols ) : array( rows )
{
for( int i = 0; i < rows; i++ )
array[ i ].resize( cols );
}
matrix( const matrix & rhs ) : array( rhs.array ) { }
const vector<Object> & operator[]( int row ) const
{ return array[ row ]; }
vector<Object> & operator[]( int row )
{ return array[ row ]; }
int numrows( ) const
{ return array.size( ); }
int numcols( ) const
{ return numrows( ) ? array[ 0 ].size( ) : 0; }
private:
vector< vector<Object> > array;
};
#endif
The #ifndef directive of the C++ Programming Language helps in allowing the conditional compilation. The C++ Programming Language's preprocessor helps in determining only if the macro provided is not at all existed before including the specific subsequent code in the C++ compilation process. The #ifndef preprocessor only checks If the specific macro is not at all defined with the help of the #define directive. If the condition is TRUE then it will be helpful in executing the code otherwise the else code of the #ifndef will be compiled or executed only if present.
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#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.
Return size. Returns the number of elements in the array container. "size()" function returns the size of the array (Note: "size()" can also be used for other containers like list etc). The size of an array object is always equal to the second template parameter used to instantiate the array template class (N). Unlike the language operator sizeof, which returns the size in bytes, this member function returns the size of the array in terms of number of elements. There is no parameter to be passed. Function returns the number of elements contained in the array object.
Templates are powerful features of C++ which allows us to write generic programs. Similar to function templates, we can use class templates to create a single class to work with different data types. Class templates come in handy as they can make our code shorter and more manageable. A class template starts with the keyword template followed by template parameter(s) inside <> which is followed by the class declaration. T is the template argument which is a placeholder for the data type used, and class is a keyword. Inside the class body, a member variable var and a member function functionName() are both of type T.
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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.
Return size. Returns the number of elements in the vector. This is the number of actual objects held in the vector, which is not necessarily equal to its storage capacity. vector::size() is a library function of "vector" header, it is used to get the size of a vector, it returns the total number of elements in the vector. The dynamic array can be created by using a vector in C++. One or more elements can be inserted into or removed from the vector at the run time that increases or decreases the size of the vector. The size or length of the vector can be counted using any loop or the built-in function named size(). This function does not accept any parameter.
A C++ template is a powerful feature added to C++. It allows you to define the generic classes and generic functions and thus provides support for generic programming. Generic programming is a technique where generic types are used as parameters in algorithms so that they can work for a variety of data types. We can define a template for a function. For example, if we have an add() function, we can create versions of the add function for adding the int, float or double type values. Where Ttype: It is a placeholder name for a data type used by the function. It is used within the function definition. It is only a placeholder that the compiler will automatically replace this placeholder with the actual data type. class: A class keyword is used to specify a generic type in a template declaration.
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.
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.
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"Aho-Corasick" string matching algorithm is a 'searching algorithm', it is a kind of dictionary matching Algorithm that locates elements of a finite set of strings (the "Dictionary") within
In this, Insert item x into the 'priority queue', maintaining heap order. Return a pointer to the node containing the new item. Find the 'smallest' item in the priority queue. Return
