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

Implementation for cursor linked list

/* Implementation for cursor linked list */ #include "CursorList.h" /** * Routine to initialize the cursorSpace. */ template <class Object> void List<Object>::initializeCursorSpace( ) { static int cursorSpaceIsInitialized = false; if( !cursorSpaceIsInitialized ) { cursorSpace.resize( 100 ); for( int i = 0; i < cursorSpace.size( ); i++ ) cursorSpace[ i ].next = i + 1; cursorSpace[ cursorSpace.size( ) - 1 ].next = 0; cursorSpaceIsInitialized = true; } } /** * Allocate a CursorNode */ template <class Object> int List<Object>::alloc( ) { int p = cursorSpace[ 0 ].next; cursorSpace[ 0 ].next = cursorSpace[ p ].next; return p; } /** * Free a CursorNode */ template <class Object> void List<Object>::free( int p ) { cursorSpace[ p ].next = cursorSpace[ 0 ].next; cursorSpace[ 0 ].next = p; } /** * Construct the list */ template <class Object> List<Object>::List( ) { initializeCursorSpace( ); header = alloc( ); cursorSpace[ header ].next = 0; } /** * Copy constructor */ template <class Object> List<Object>::List( const List<Object> & rhs ) { initializeCursorSpace( ); header = alloc( ); cursorSpace[ header ].next = 0; *this = rhs; } /** * Destroy the list */ template <class Object> List<Object>::~List( ) { makeEmpty( ); free( header ); } /** * Test if the list is logically empty. * return true if empty, false otherwise. */ template <class Object> bool List<Object>::isEmpty( ) const { return cursorSpace[ header ].next == 0; } /** * Make the list logically empty. */ template <class Object> void List<Object>::makeEmpty( ) { while( !isEmpty( ) ) remove( first( ).retrieve( ) ); } /** * Return an iterator representing the header node. */ template <class Object> ListItr<Object> List<Object>::zeroth( ) const { return ListItr<Object>( header ); } /** * Return an iterator representing the first node in the list. * This operation is valid for empty lists. */ template <class Object> ListItr<Object> List<Object>::first( ) const { return ListItr<Object>( cursorSpace[ header ].next ); } /** * Insert item x after p. */ template <class Object> void List<Object>::insert( const Object & x, const ListItr<Object> & p ) { if( p.current != 0 ) { int pos = p.current; int tmp = alloc( ); cursorSpace[ tmp ] = CursorNode( x, cursorSpace[ pos ].next ); cursorSpace[ pos ].next = tmp; } } /** * Return iterator corresponding to the first node containing an item x. * Iterator isPastEnd if item is not found. */ template <class Object> ListItr<Object> List<Object>::find( const Object & x ) const { /* 1*/ int itr = cursorSpace[ header ].next; /* 2*/ while( itr != 0 && cursorSpace[ itr ].element != x ) /* 3*/ itr = cursorSpace[ itr ].next; /* 4*/ return ListItr<Object>( itr ); } /** * Return iterator prior to the first node containing an item x. */ template <class Object> ListItr<Object> List<Object>::findPrevious( const Object & x ) const { /* 1*/ int itr = header; /* 2*/ while( cursorSpace[ itr ].next != 0 && cursorSpace[ cursorSpace[ itr ].next ].element != x ) /* 3*/ itr = cursorSpace[ itr ].next; /* 4*/ return ListItr<Object>( itr ); } /** * Remove the first occurrence of an item x. */ template <class Object> void List<Object>::remove( const Object & x ) { ListItr<Object> p = findPrevious( x ); int pos = p.current; if( cursorSpace[ pos ].next != 0 ) { int tmp = cursorSpace[ pos ].next; cursorSpace[ pos ].next = cursorSpace[ tmp ].next; free ( tmp ); } } /** * Deep copy of linked lists. */ template <class Object> const List<Object> & List<Object>::operator=( const List<Object> & rhs ) { ListItr<Object> ritr = rhs.first( ); ListItr<Object> itr = zeroth( ); if( this != &rhs ) { makeEmpty( ); for( ; !ritr.isPastEnd( ); ritr.advance( ), itr.advance( ) ) insert( ritr.retrieve( ), itr ); } return *this; }

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.

The pointer in C++ language is a variable, it is also known as locator or indicator that points to an address of a value. In C++, a pointer refers to a variable that holds the address of another variable. Like regular variables, pointers have a data type. For example, a pointer of type integer can hold the address of a variable of type integer. A pointer of character type can hold the address of a variable of character type. You should see a pointer as a symbolic representation of a memory address. With pointers, programs can simulate call-by-reference. They can also create and manipulate dynamic data structures. In C++, a pointer variable refers to a variable pointing to a specific address in a memory pointed by another variable.

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.

List is a popularly used sequence container. Container is an object that holds data of same type. List container is implemented as doubly linked-list, hence it provides bidirectional sequential access to it's data. List doesn't provide fast random access, it only supports sequential access in both directions. List allows insertion and deletion operation anywhere within a sequence in constant time. Elements of list can be scattered in different chunks of memory. Container stores necessary information to allow sequential access to it's data. Lists can shrink or expand as needed from both ends at run time. The storage requirement is fulfilled automatically by internal allocator. Zero sized lists are also valid. In that case list.begin() and list.end() points to same location. But behavior of calling front() or back() is undefined. To define the std::list, we have to import the <list> header file.

In while loop, condition is evaluated first and if it returns true then the statements inside while loop execute, this happens repeatedly until the condition returns false. When condition returns false, the control comes out of loop and jumps to the next statement in the program after while loop. The important point to note when using while loop is that we need to use increment or decrement statement inside while loop so that the loop variable gets changed on each iteration, and at some point condition returns false. This way we can end the execution of while loop otherwise the loop would execute indefinitely. A while loop that never stops is said to be the infinite while loop, when we give the condition in such a way so that it never returns false, then the loops becomes infinite and repeats itself indefinitely.

Logical Operators are used to compare and connect two or more expressions or variables, such that the value of the expression is completely dependent on the original expression or value or variable. We use logical operators to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0. Assume variable A holds 1 and variable B holds 0:

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.

Every object in C++ has access to its own address through an important pointer called this pointer. The this pointer is an implicit parameter to all member functions. Therefore, inside a member function, this may be used to refer to the invoking object. Friend functions do not have a this pointer, because friends are not members of a class. Only member functions have a this pointer. In C++ programming, this is a keyword that refers to the current instance of the class. There can be 3 main usage of this keyword in C++: • It can be used to pass current object as a parameter to another method. • It can be used to refer current class instance variable. • It can be used to declare indexers. To understand 'this' pointer, it is important to know how objects look at functions and data members of a class.

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.

A destructor is a special member function that works just opposite to constructor, unlike constructors that are used for initializing an object, destructors destroy (or delete) the object. Destructors in C++ are members functions in a class that delete an object. They are called when the class object goes out of scope such as when the function ends, the program ends, a delete variable is called etc. Destructors are different from normal member functions as they don't take any argument and don't return anything. Also, destructors have the same name as their class and their name is preceded by a tilde(~).

#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.

Advance iterator. Advances the iterator it by n element positions. If it is a random-access iterator, the function uses just once operator+ or operator-. Otherwise, the function uses repeatedly the increase or decrease operator (operator++ or operator--) until n elements have been advanced. This function does not return any value.

In C++, classes and structs are blueprints that are used to create the instance of a class. Structs are used for lightweight objects such as Rectangle, color, Point, etc. Unlike class, structs in C++ are value type than reference type. It is useful if you have data that is not intended to be modified after creation of struct. C++ Structure is a collection of different data types. It is similar to the class that holds different types of data. A structure is declared by preceding the struct keyword followed by the identifier(structure name). Inside the curly braces, we can declare the member variables of different types.

Iterators are just like pointers used to access the container elements. Iterators are one of the four pillars of the Standard Template Library or STL in C++. An iterator is used to point to the memory address of the STL container classes. For better understanding, you can relate them with a pointer, to some extent. Iterators act as a bridge that connects algorithms to STL containers and allows the modifications of the data present inside the container. They allow you to iterate over the container, access and assign the values, and run different operators over them, to get the desired result. • Iterators are used to traverse from one element to another element, a process is known as iterating through the container. • The main advantage of an iterator is to provide a common interface for all the containers type. • Iterators make the algorithm independent of the type of the container used.

Static is a keyword in C++ used to give special characteristics to an element. Static elements are allocated storage only once in a program lifetime in static storage area. And they have a scope till the program lifetime. In C++, static is a keyword or modifier that belongs to the type not instance. So instance is not required to access the static members. In C++, static can be field, method, constructor, class, properties, operator and event. Advantage of C++ static keyword: Memory efficient. Now we don't need to create instance for accessing the static members, so it saves memory. Moreover, it belongs to the type, so it will not get memory each time when instance is created.

Deallocate memory block. A block of memory previously allocated by a call to malloc, calloc or realloc is deallocated, making it available again for further allocations. If ptr does not point to a block of memory allocated with the above functions, it causes undefined behavior. If ptr is a null pointer, the function does nothing. Notice that this function does not change the value of ptr itself, hence it still points to the same (now invalid) location. free() function in C++ <cstdlib> library is used to deallocate a memory block in C++. Whenever we call malloc, calloc or realloc function to allocate a memory block dynamically in C++, compiler allocates a block of size bytes of memory and returns a pointer to the start of the block. The new memory block allocated is not initialized but have intermediate values. free() method is used to free such block of memory. In case the pointer mentioned does not point to any memory block then it may lead to an undefined behavior, but does nothing in case of null

"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

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