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C++ Programming Code Examples

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

Implementation for stack - array version

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/* Implementation for stack - array version */ #include "StackAr.h" /** * Construct the stack. */ template <class Object> Stack<Object>::Stack( int capacity ) : theArray( capacity ) { topOfStack = -1; } /** * Test if the stack is logically empty. * Return true if empty, false otherwise. */ template <class Object> bool Stack<Object>::isEmpty( ) const { return topOfStack == -1; } /** * Test if the stack is logically full. * Return true if full, false otherwise. */ template <class Object> bool Stack<Object>::isFull( ) const { return topOfStack == theArray.size( ) - 1; } /** * Make the stack logically empty. */ template <class Object> void Stack<Object>::makeEmpty( ) { topOfStack = -1; } /** * Get the most recently inserted item in the stack. * Does not alter the stack. * Return the most recently inserted item in the stack. * Exception Underflow if stack is already empty. */ template <class Object> const Object & Stack<Object>::top( ) const { if( isEmpty( ) ) throw Underflow( ); return theArray[ topOfStack ]; } /** * Remove the most recently inserted item from the stack. * Exception Underflow if stack is already empty. */ template <class Object> void Stack<Object>::pop( ) { if( isEmpty( ) ) throw Underflow( ); topOfStack--; } /** * Insert x into the stack, if not already full. * Exception Overflow if stack is already full. */ template <class Object> void Stack<Object>::push( const Object & x ) { if( isFull( ) ) throw Overflow( ); theArray[ ++topOfStack ] = x; } /** * Return and remove most recently inserted item from the stack. * Return most recently inserted item. * Exception Underflow if stack is already empty. */ template <class Object> Object Stack<Object>::topAndPop( ) { if( isEmpty( ) ) throw Underflow( ); return theArray[ topOfStack-- ]; }
Stack Library size() Function in C++
Return size. Returns the number of elements in the stack. stack::size() function is an inbuilt function in C++ STL, which is defined in <stack>header file. size() is used to check the associated container's size and return the result in an integer value, which is the number of elements in the container. If the container is empty the size() returns 0 This member function effectively calls member size of the underlying container object.
Syntax for Stack size() Function in C++
#include <stack> size_type size() const;
No parameter is required. Function returns the number of elements in the underlying container. Member type size_type is an unsigned integral type.
Constant (calling size on the underlying container).
Data races
The container is accessed
Exception safety
Provides the same level of guarantees as the operation performed on the container (no-throw guarantee for standard container types).
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/* C++ Stack size() function returns the number of stack elements. The number of stack elements is referred to the size of the stack. The size of the stack element is very important information as based on it we can deduce many other things such as the space required, etc. */ /* Find out the total number of elements in the stack by stack::size function code example. */ #include <iostream> #include <stack> using namespace std; int main (){ stack<int> MyStack; MyStack.push(10); MyStack.push(20); MyStack.push(30); MyStack.push(40); MyStack.push(50); cout<<"Stack size is: "<<MyStack.size()<<"\n"; cout<<"Three elements are added in the Stack.\n"; MyStack.push(60); MyStack.push(70); MyStack.push(80); cout<<"Now, Stack size is: "<<MyStack.size()<<"\n"; return 0; }
If Else Statement in C++
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,
Syntax for If Statement in C++
if (condition) { // body of if 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.
Syntax for If...Else Statement
if (condition) { // block of code if condition is true } else { // block of code if condition is false }
The if..else statement evaluates the condition inside the parenthesis. If the condition evaluates true, the code inside the body of if is executed, the code inside the body of else is skipped from execution. If the condition evaluates false, the code inside the body of else is executed, the code inside the body of if is skipped from execution. The if...else statement is used to execute a block of code among two alternatives. However, if we need to make a choice between more than two alternatives, we use the if...else if...else statement.
Syntax for If...Else...Else If Statement in C++
if (condition1) { // code block 1 } else if (condition2){ // code block 2 } else { // code block 3 }
• If condition1 evaluates to true, the code block 1 is executed. • If condition1 evaluates to false, then condition2 is evaluated. • If condition2 is true, the code block 2 is executed. • If condition2 is false, the code block 3 is executed. There can be more than one else if statement but only one if and else statements. In C/C++ if-else-if ladder helps user decide from among multiple options. The C/C++ if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C else-if ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
Syntax for If Else If Ladder in C++
if (condition) statement 1; else if (condition) statement 2; . . else statement;
Working of the if-else-if ladder: 1. Control falls into the if block. 2. The flow jumps to Condition 1. 3. Condition is tested. If Condition yields true, goto Step 4. If Condition yields false, goto Step 5. 4. The present block is executed. Goto Step 7. 5. The flow jumps to Condition 2. If Condition yields true, goto step 4. If Condition yields false, goto Step 6. 6. The flow jumps to Condition 3. If Condition yields true, goto step 4. If Condition yields false, execute else block. Goto Step 7. 7. Exits the if-else-if ladder. • The if else ladder statement in C++ programming language is used to check set of conditions in sequence. • This is useful when we want to selectively executes one code block(out of many) based on certain conditions. • It allows us to check for multiple condition expressions and execute different code blocks for more than two conditions. • A condition expression is tested only when all previous if conditions in if-else ladder is false. • If any of the conditional expression evaluates to true, then it will execute the corresponding code block and exits whole if-else ladder.
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/* If Else Statement in C++ Language */ #include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a < 20 ) { // if condition is true then print the following cout << "a is less than 20;" << endl; } else { // if condition is false then print the following cout << "a is not less than 20;" << endl; } cout << "value of a is : " << a << endl; return 0; }
#include Directive in C++
#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.
Syntax for #include Directive in C++
#include "user-defined_file"
Including using " ": When using the double quotes(" "), the preprocessor access the current directory in which the source "header_file" is located. This type is mainly used to access any header files of the user's program or user-defined files.
#include <header_file>
Including using <>: While importing file using angular brackets(<>), the the preprocessor uses a predetermined directory path to access the file. It is mainly used to access system header files located in the standard system directories. Header File or Standard files: This is a file which contains C/C++ function declarations and macro definitions to be shared between several source files. Functions like the printf(), scanf(), cout, cin and various other input-output or other standard functions are contained within different header files. So to utilise those functions, the users need to import a few header files which define the required functions. User-defined files: These files resembles the header files, except for the fact that they are written and defined by the user itself. This saves the user from writing a particular function multiple times. Once a user-defined file is written, it can be imported anywhere in the program using the #include preprocessor. • In #include directive, comments are not recognized. So in case of #include <a//b>, a//b is treated as filename. • In #include directive, backslash is considered as normal text not escape sequence. So in case of #include <a\nb>, a\nb is treated as filename. • You can use only comment after filename otherwise it will give error.
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/* using #include directive in C language */ #include <stdio.h> int main() { /* * C standard library printf function * defined in the stdio.h header file */ printf("I love you Clementine"); printf("I love you so much"); printf("HappyCodings"); return 0; }
Class Templates in C++
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.
Declaration for Class Template in C++
template <class T> class className { private: T var; ... .. ... public: T functionName(T arg); ... .. ... };
template argument
a member variable 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. Creating a class template object: Once we've declared and defined a class template, we can create its objects in other classes or functions (such as the main() function) with the following syntax:
className<dataType> classObject;
Defining a class member outside the class template: Suppose we need to define a function outside of the class template. We can do this with the following code:
template <class T> class ClassName { ... .. ... // Function prototype returnType functionName(); }; // Function definition template <class T> returnType ClassName<T>::functionName() { // code }
Notice that the code template <class T> is repeated while defining the function outside of the class. This is necessary and is part of the syntax. C++ class templates with multiple parameters: In C++, we can use multiple template parameters and even use default arguments for those parameters.
template <class T, class U, class V = int> class ClassName { private: T member1; U member2; V member3; ... .. ... public: ... .. ... };
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/* Templates are the foundation of generic programming, which involves writing code in a way that is independent of any particular type. A template is a blueprint or formula for creating a generic class or a function. */ #include <iostream> using namespace std; template <typename T> class Array { private: T *ptr; int size; public: Array(T arr[], int s); void print(); }; template <typename T> Array<T>::Array(T arr[], int s) { ptr = new T[s]; size = s; for(int i = 0; i < size; i++) ptr[i] = arr[i]; } template <typename T> void Array<T>::print() { for (int i = 0; i < size; i++) cout<<" "<<*(ptr + i); cout<<endl; } int main() { int arr[5] = {1, 2, 3, 4, 5}; Array<int> a(arr, 5); a.print(); return 0; }
Function Templates in C++
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.
Syntax for Function Templates in C++
template < class Ttype> ret_type func_name(parameter_list) { // body of function. }
a placeholder name
specify a generic type 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. • Generic functions use the concept of a function template. Generic functions define a set of operations that can be applied to the various types of data. • The type of the data that the function will operate on depends on the type of the data passed as a parameter. • For example, Quick sorting algorithm is implemented using a generic function, it can be implemented to an array of integers or array of floats. • A Generic function is created by using the keyword template. The template defines what function will do. Function templates with multiple parameters: We can use more than one generic type in the template function by using the comma to separate the list.
template<class T1, class T2,.....> return_type function_name (arguments of type T1, T2....) { // body of function. }
Overloading a function template: We can overload the generic function means that the overloaded template functions can differ in the parameter list. Generic functions perform the same operation for all the versions of a function except the data type differs.
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/* function templates in C++ language */ /* adding two numbers using function templates */ #include <iostream> using namespace std; template <typename T> T add(T num1, T num2) { return (num1 + num2); } int main() { int result1; double result2; // calling with int parameters result1 = add<int>(2, 3); cout << "2 + 3 = " << result1 << endl; // calling with double parameters result2 = add<double>(2.2, 3.3); cout << "2.2 + 3.3 = " << result2 << endl; return 0; }
What is an Array in C++ Language
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. By using the array, we can access the elements easily. Only a few lines of code are required to access the elements of the array.
Properties of Array
The array contains the following properties. • Each element of an array is of same data type and carries the same size, i.e., int = 4 bytes. • Elements of the array are stored at contiguous memory locations where the first element is stored at the smallest memory location. • Elements of the array can be randomly accessed since we can calculate the address of each element of the array with the given base address and the size of the data element.
Advantage of C++ Array
• 1) Code Optimization: Less code to the access the data. • 2) Ease of traversing: By using the for loop, we can retrieve the elements of an array easily. • 3) Ease of sorting: To sort the elements of the array, we need a few lines of code only. • 4) Random Access: We can access any element randomly using the array.
Disadvantage of C++ Array
• 1) Allows a fixed number of elements to be entered which is decided at the time of declaration. Unlike a linked list, an array in C++ is not dynamic. • 2) Insertion and deletion of elements can be costly since the elements are needed to be managed in accordance with the new memory allocation.
Declaration of C++ Array
To declare an array in C++, a programmer specifies the type of the elements and the number of elements required by an array as follows
type arrayName [ arraySize ];
This is called a single-dimensional array. The arraySize must be an integer constant greater than zero and type can be any valid C++ data type. For example, to declare a 10-element array called balance of type double, use this statement
double balance[10];
Here balance is a variable array which is sufficient to hold up to 10 double numbers.
Initializing Arrays
You can initialize an array in C++ either one by one or using a single statement as follows
double balance[5] = {850, 3.0, 7.4, 7.0, 88};
The number of values between braces { } cannot be larger than the number of elements that we declare for the array between square brackets [ ]. If you omit the size of the array, an array just big enough to hold the initialization is created. Therefore, if you write
double balance[] = {850, 3.0, 7.4, 7.0, 88};
Accessing Array Elements
An element is accessed by indexing the array name. This is done by placing the index of the element within square brackets after the name of the array.
double salary = balance[9];
The above statement will take the 10th element from the array and assign the value to salary variable.
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/* arrays in C++ Language */ #include <iostream> using namespace std; int main() { // initialize an array without specifying size double numbers[] = {7, 5, 6, 12, 35, 27}; double sum = 0; double count = 0; double average; cout << "The numbers are: "; // print array elements // use of range-based for loop for (const double &n : numbers) { cout << n << " "; // calculate the sum sum += n; // count the no. of array elements ++count; } // print the sum cout << "\nTheir Sum = " << sum << endl; // find the average average = sum / count; cout << "Their Average = " << average << endl; return 0; }
Structures in C++ Language
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.
Syntax for Structures in C++
struct structureName{ member1; member2; member3; . . . memberN; };
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. Consider the following situation:
struct Teacher { char name[20]; int id; int age; }
In the above case, Teacher is a structure contains three variables name, id, and age. When the structure is declared, no memory is allocated. When the variable of a structure is created, then the memory is allocated. Let's understand this scenario. Structures in C++ can contain two types of members: • Data Member: These members are normal C++ variables. We can create a structure with variables of different data types in C++. • Member Functions: These members are normal C++ functions. Along with variables, we can also include functions inside a structure declaration. Structure variable can be defined as: Teacher s; Here, s is a structure variable of type Teacher. When the structure variable is created, the memory will be allocated. Teacher structure contains one char variable and two integer variable. Therefore, the memory for one char variable is 1 byte and two ints will be 2*4 = 8. The total memory occupied by the s variable is 9 byte. The variable of the structure can be accessed by simply using the instance of the structure followed by the dot (.) operator and then the field of the structure.
s.id = 4;
We are accessing the id field of the structure Teacher by using the dot(.) operator and assigns the value 4 to the id field. In C++, the struct keyword is optional before in declaration of a variable. In C, it is mandatory.
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/* Structure is a collection of variables of different data types under a single name. It is similar to a class in that, both holds a collecion of data of different data types. */ #include <iostream> using namespace std; struct Person { char name[50]; int age; float salary; }; int main() { Person p1; cout << "Enter Full name: "; cin.get(p1.name, 50); cout << "Enter age: "; cin >> p1.age; cout << "Enter salary: "; cin >> p1.salary; cout << "\nDisplaying Information." << endl; cout << "Name: " << p1.name << endl; cout <<"Age: " << p1.age << endl; cout << "Salary: " << p1.salary; return 0; }
Stack push() Function in C++
Insert element. Inserts a new element at the top of the stack, above its current top element. The content of this new element is initialized to a copy of val. This member function effectively calls the member function push_back of the underlying container object. C++ Stack push () function is used for adding new elements at the top of the stack. If we have an array of type stack and by using the push() function we can insert new elements in the stack. The elements are inserted at the top of the stack. The element which is inserted most initially is deleted at the end and vice versa as stacks follow LIFO principle.
Syntax for Stack push() Function in C++
void push (const value_type& val); void push (value_type&& val);
Value to which the inserted element is initialized. Member type value_type is the type of the elements in the container (defined as an alias of the first class template parameter, T). The function only inserts element and does not return any value. The return type of the function can be thought as void.
One call to push_back on the underlying container.
Data races
The container and up to all its contained elements are modified.
Exception safety
Provides the same level of guarantees as the operation performed on the underlying container object.
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/* demonstrate the use of the push() function of the stack by insertion of simple integer values */ #include <iostream> #include <stack> int main() { std::stack<int> newstack; newstack.push(11); newstack.push(22); newstack.push(33); newstack.push(44); std::cout << "Popping out elements?"; newstack.pop(); newstack.pop(); while (!newstack.empty () ) { std::cout << " " << newstack.top(); newstack.pop(); } std:: cout<<'\n'; return 0; }
Stack in C++ Language
LIFO stack. Stacks are a type of container adaptor, specifically designed to operate in a LIFO context (last-in first-out), where elements are inserted and extracted only from one end of the container. stacks are implemented as container adaptors, which are classes that use an encapsulated object of a specific container class as its underlying container, providing a specific set of member functions to access its elements. Elements are pushed/popped from the "back" of the specific container, which is known as the top of the stack.
Syntax for Stack in C++
template <class T, class Container = deque<T> > class stack;
Type of the elements. Aliased as member type stack::value_type.
Type of the internal underlying container object where the elements are stored. Its value_type shall be T. Aliased as member type stack::container_type.
Member types
value_type The first template parameter (T) Type of the elements container_type The second template parameter (Container) Type of the underlying container reference container_type::reference usually, value_type& const_reference container_type::const_reference usually, const value_type& size_type an unsigned integral type usually, the same as size_t
Member functions
(constructor) Construct stack (public member function ) stack::emplace: Constructs and inserts new element at the top of stack. stack::empty: Tests whether stack is empty or not. stack::operator= copy version: Assigns new contents to the stack by replacing old ones. stack::operator= move version: Assigns new contents to the stack by replacing old ones. stack::pop: Removes top element from the stack. stack::push copy version: Inserts new element at the top of the stack. stack::push move version: Inserts new element at the top of the stack. stack::size: Returns the total number of elements present in the stack. stack::swap: Exchanges the contents of stack with contents of another stack. stack::top: Returns a reference to the topmost element of the stack.
Non-member function overloads
relational operators Relational operators for stack (function ) swap (stack) Exchange contents of stacks (public member function ) operator==: Tests whether two stacks are equal or not. operator!=: Tests whether two stacks are equal or not. operator<: Tests whether first stack is less than other or not. operator<=: Tests whether first stack is less than or equal to other or not. operator>: Tests whether first stack is greater than other or not. operator>=: Tests whether first stack is greater than or equal to other or not.
Non-member class specializations
uses_allocator<stack> Uses allocator for stack (class template ) The standard container classes vector, deque and list fulfill these requirements. By default, if no container class is specified for a particular stack class instantiation, the standard container deque is used. Stack is a data structure designed to operate in LIFO (Last in First out) context. In stack elements are inserted as well as get removed from only one end. Stack class is container adapter. Container is an objects that hold data of same type. Stack can be created from different sequence containers. If container is not provided it uses default deque container. Container adapters do not support iterators therefore we cannot use them for data manipulation. However they support push() and pop() member functions for data insertion and removal respectively.
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/* Stack in C++ language */ #include <iostream> #include <stack> using namespace std; void newstack(stack <int> ss) { stack <int> sg = ss; while (!sg.empty()) { cout << '\t' << sg.top(); sg.pop(); } cout << '\n'; } int main () { stack <int> newst; newst.push(55); newst.push(44); newst.push(33); newst.push(22); newst.push(11); cout << "The stack newst is : "; newstack(newst); cout << "\n newst.size() : " << newst.size(); cout << "\n newst.top() : " << newst.top(); cout << "\n newst.pop() : "; newst.pop(); newstack(newst); return 0; }

Function will return 0, if the strings are equal; return 'negative value', if "string1 is less" than string2 and return "positive value" if string1 is greater than string2. This function 'compares'
C++ Program to generate N passwords each of 'length M'. Problem focuses on finding the N permutations each of length M. Generates random number between 1 and 10. Enter the