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C++ Programming Code Examples

C++ > Code Snippets Code Examples

Set cout to output hex number

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/* Set cout to output hex number */ #include <iostream> #include <iomanip> using namespace std; int main() { const int number = 185; cout << "The number is " << number << endl; cout << "The number is " << hex << number << endl; cout.setf(ios::showbase); cout << "The number is " << hex << number << endl; cout << "The number is " ; cout.width(10); cout << hex << number << endl; cout << "The number is " ; cout.width(10); cout.setf(ios::left); cout << hex << number << endl; cout << "The number is " ; cout.width(10); cout.setf(ios::internal); cout << hex << number << endl; cout << "The number is " << setw(10) << hex << number << endl; return 0; }
Return Statement in C++
A return statement ends the processing of the current function and returns control to the caller of the function. A value-returning function should include a return statement, containing an expression. If an expression is not given on a return statement in a function declared with a non-void return type, the compiler issues an error message. If the data type of the expression is different from the function return type, conversion of the return value takes place as if the value of the expression were assigned to an object with the same function return type.
Syntax for Return Statement in C++
return[expression];
For a function of return type void, a return statement is not strictly necessary. If the end of such a function is reached without encountering a return statement, control is passed to the caller as if a return statement without an expression were encountered. In other words, an implicit return takes place upon completion of the final statement, and control automatically returns to the calling function. If a return statement is used, it must not contain an expression. The following are examples of return statements:
return; /* Returns no value */ return result; /* Returns the value of result */ return 1; /* Returns the value 1 */ return (x * x); /* Returns the value of x * x */
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/* illustrate Methods returning a value using return statement in C++ code example */ #include <iostream> using namespace std; // non-void return type // function to calculate sum int SUM(int a, int b) { int s1 = a + b; // method using the return // statement to return a value return s1; } // Driver method int main() { int num1 = 10; int num2 = 10; int sum_of = SUM(num1, num2); cout << "The sum is " << sum_of; return 0; }
Iomanip Library setw() Function in C++
Set field width. Sets the field width to be used on output operations. The C++ function std::setw behaves as if member width were called with n as argument on the stream on which it is inserted/extracted as a manipulator (it can be inserted/extracted on input streams or output streams). It is used to sets the field width to be used on output operations. This manipulator is declared in header <iomanip>.
Syntax for setw() Function in C++
#include <iomanip> /*undefined*/ setw (int n);
n
Number of characters to be used as field width. This method accepts n as a parameter which is the integer argument corresponding to which the field width is to be set. This function returns an object of unspecified type. The setw function should only be used as a stream manipulator. Like the different functions in C++ the setw() function helps in setting the field width which will be used on output operations. This function will take the member width whenever it will be called as an argument. It will need a stream where this field will be inserted or manipulated. This function will set the width parameter of the stream out or stream in to exactly n times. It will take the parameter which will be the new value of the width to which this has to be set.
Data races
The stream object on which it is inserted/extracted is modified. Concurrent access to the same stream object may introduce data races.
Exception safety
Basic guarantee: if an exception is thrown, the stream is in a valid state.
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/* specify the minimum number of character positions on the output field a variable will consume by setw function() code example. */ // C++ code to demonstrate the working of setw() function #include <iomanip> #include <ios> #include <iostream> using namespace std; int main() { // Initializing the integer int num = 50; cout << "Before setting the width: \n" << num << endl; // Using setw() cout << "Setting the width" << " using setw to 5: \n" << setw(5); cout << num << endl; return 0; }
Namespaces in C++ Language
Consider a situation, when we have two persons with the same name, jhon, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother's or father's name, etc. Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function you are referring to within your code. A namespace is designed to overcome this difficulty and is used as additional information to differentiate similar functions, classes, variables etc. with the same name available in different libraries. Using namespace, you can define the context in which names are defined. In essence, a namespace defines a scope.
Defining a Namespace
A namespace definition begins with the keyword namespace followed by the namespace name as follows:
namespace namespace_name { // code declarations }
To call the namespace-enabled version of either function or variable, prepend (::) the namespace name as follows:
name::code; // code could be variable or function.
Using Directive
You can also avoid prepending of namespaces with the using namespace directive. This directive tells the compiler that the subsequent code is making use of names in the specified namespace.
Discontiguous Namespaces
A namespace can be defined in several parts and so a namespace is made up of the sum of its separately defined parts. The separate parts of a namespace can be spread over multiple files. So, if one part of the namespace requires a name defined in another file, that name must still be declared. Writing a following namespace definition either defines a new namespace or adds new elements to an existing one:
namespace namespace_name { // code declarations }
Nested Namespaces
Namespaces can be nested where you can define one namespace inside another name space as follows:
namespace namespace_name1 { // code declarations namespace namespace_name2 { // code declarations } }
• Namespace is a feature added in C++ and not present in C. • A namespace is a declarative region that provides a scope to the identifiers (names of the types, function, variables etc) inside it. • Multiple namespace blocks with the same name are allowed. All declarations within those blocks are declared in the named scope. • Namespace declarations appear only at global scope. • Namespace declarations can be nested within another namespace. • Namespace declarations don't have access specifiers. (Public or private) • No need to give semicolon after the closing brace of definition of namespace. • We can split the definition of namespace over several units.
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/* namespaces in C++ language */ // A C++ code to demonstrate that we can define // methods outside namespace. #include <iostream> using namespace std; // Creating a namespace namespace ns { void display(); class happy { public: void display(); }; } // Defining methods of namespace void ns::happy::display() { cout << "ns::happy::display()\n"; } void ns::display() { cout << "ns::display()\n"; } // Driver code int main() { ns::happy obj; ns::display(); obj.display(); return 0; }
Standard Output Stream (cout) in C++
The cout is a predefined object of ostream class. It is connected with the standard output device, which is usually a display screen. The cout is used in conjunction with stream insertion operator (<<) to display the output on a console. On most program environments, the standard output by default is the screen, and the C++ stream object defined to access it is cout.
Syntax for cout in C++
cout << var_name; //or cout << "Some String";
The syntax of the cout object in C++: cout << var_name; Or cout << "Some String";
<<
is the insertion operator
var_name
is usually a variable, but can also be an array element or elements of containers like vectors, lists, maps, etc. The "c" in cout refers to "character" and "out" means "output". Hence cout means "character output". The cout object is used along with the insertion operator << in order to display a stream of characters. The << operator can be used more than once with a combination of variables, strings, and manipulators. cout is used for displaying data on the screen. The operator << called as insertion operator or put to operator. The Insertion operator can be overloaded. Insertion operator is similar to the printf() operation in C. cout is the object of ostream class. Data flow direction is from variable to output device. Multiple outputs can be displayed using cout.
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/* standard output stream (cout) in C++ language */ #include <iostream> using namespace std; int main() { string str = "Do not interrupt me"; char ch = 'm'; // use cout with write() cout.write(str,6); cout << endl; // use cout with put() cout.put(ch); return 0; }
width() Function in C++
Get/set field width. The first form (1) returns the current value of the field width. The second form (2) also sets a new field width for the stream. The field width determines the minimum number of characters to be written in some output representations. If the standard width of the representation is shorter than the field width, the representation is padded with fill characters at a point determined by the format flag adjustfield (one of left, right or internal). The fill character can be retrieved or changed by calling the member function fill. The format flag adjustfield can be modified by calling the member functions flags or setf, by inserting one of the following manipulators: left, right and internal, or by inserting the parameterized manipulator setiosflags. The field width can also be modified using the parameterized manipulator setw. Manages the minimum number of characters to generate on certain output operations and the maximum number of characters to generate on certain input operations. Returns the current field width. Sets the field width to the given one. Returns the previous field width.
Syntax for width() Function in C++
//get (1) streamsize width() const; //set (2) streamsize width (streamsize wide);
wide
New value for the stream's field width. streamsize in signed integral type. Function returns the value of the field width before the call. Some I/O functions call width(0) before returning, see std::setw (this results in this field having effect on the next I/O function only, and not on any subsequent I/O) The exact effects this modifier has on the input and output vary between the individual I/O functions and are described at each operator<< and operator>> overload page individually.
Data races
Accesses (1) or modifies (2) the stream object. Concurrent access to the same stream object may cause data races.
Exception safety
Basic guarantee: if an exception is thrown, the stream is in a valid state.
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/* returns the current width, which is defined as the minimum number of characters to display with each output by function width() code example. */ //Adjusting the width of output #include <iostream.h> int main() { cout << "Start >"; cout.width(25); cout << 123 << "< End\n"; cout << "Start >"; cout.width(25); cout << 123<< "< Next >"; cout << 456 << "< End\n"; cout << "Start >"; cout.width(4); cout << 123456 << "< End\n"; return 0; }
setf() Function in C++
Set specific format flags. The function setf() sets the io stream format flags of the current stream to fmtfl. The optional mask argument specifies that only the flags that are in both fmtfl and mask should be set. The return value is the previous configuration of io stream format flags.
Syntax for setf() Function in C++
#include <iostream> /* set (1) */ fmtflags setf (fmtflags fmtfl); /* mask (2) */ fmtflags setf (fmtflags fmtfl, fmtflags mask);
fmtfl
Format flags to be set. If the second syntax is used, only the bits set in both fmtfl and mask are set in the stream's format flags; the flags set in mask but not in fmtfl are cleared.
mask
Mask containing the flags to be modified. Member type fmtflags is a bitmask type (see ios_base::fmtflags). Function returns the format flags selected in the stream before the call. The first form (1) sets the stream's format flags whose bits are set in fmtfl, leaving unchanged the rest, as if a call to flags(fmtfl|flags()). The second form (2) sets the stream's format flags whose bits are set in both fmtfl and mask, and clears the format flags whose bits are set in mask but not in fmtfl, as if a call to flags((fmtfl&mask)|(flags()&~mask)). Both return the value of the stream's format flags before the call. The format flags of a stream affect the way data is interpreted in certain input functions and how it is written by certain output functions. See ios_base::fmtflags for the possible values of this function's arguments. The first form of setf (1) is generally used to set independent format flags: boolalpha, showbase, showpoint, showpos, skipws, unitbuf and uppercase, which can also be unset directly with member unsetf. The second form (2) is generally used to set a value for one of the selective flags, using one of the field bitmasks as the mask argument: fmtfl (format flag value) mask (field bitmask) left, right or internal adjustfield dec, oct or hex basefield scientific or fixed floatfield Flags for setf() function: ios::dec -- use decimal base for integer I/O ios::oct -- use octal base for integer I/O ios::hex -- use hexadecimal base for integer I/O ios::basefield -- dec|oct|hex. Useful for masking operations ios::internal -- internal adjustment (adds fill characters to the internal designated point) ios::adjustfield -- left|right|internal. Useful for masking operations ios::floatfield -- scientific|fixed. Useful for masking operations ios::boolalpha -- insert and extract bool type in alphanumeric format ios::showbase -- generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O ios::showpos -- generate a + character for non-negative numeric output ios::skipws -- skip leading whitespace before certain input operations ios::unitbuf -- flush the output after each output operation ios::uppercase -- replace certain lowercase letters with their uppercase equivalents in certain output operations ios::fixed -- to specify that floating-point numbers will be printed in fixed notation. ios::scientific -- to specify that floating-point numbers will be printed in scientific (exponential) notation. ios::showpoint -- specifies that the decimal point will always be printed for floating point types (even if the value is a whole number, like 4.0. ios::right -- right-justifies an output item in a field, if a field width is specified. ios::left -- left-justifies an output item in a field, if a field width is specified.
Data races
Modifies the stream object. Concurrent access to the same stream object may cause data races.
Exception safety
Basic guarantee: if an exception is thrown, the stream is in a valid state.
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/* set specific format flags by setf() function code example */ #include <iostream> using namespace std; int main(void){ cout << true << " " << false << endl; cout.setf(ios_base::boolalpha); cout << true << " " << false << endl; cout << 192.168 << " "; cout.setf(ios_base::scientific, ios_base::floatfield); cout << 192.168 << endl; cout.width(30); cout << "Saluton, Mundo!" << endl; cout.setf(ios_base::left, ios_base::adjustfield); cout.width(30); cout << "Saluton, Mundo!" << endl; return 0; }
main() Function in C++
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.
Syntax for main() Function in C++
void main() { ............ ............ }
void
void is a keyword in C++ language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value.
main
main is a name of function which is predefined function in C++ library. In place of void we can also use int return type of main() function, at that time main() return integer type value. 1) It cannot be used anywhere in the program a) in particular, it cannot be called recursively b) its address cannot be taken 2) It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace). 3) It cannot be defined as deleted or (since C++11) declared with C language linkage, constexpr (since C++11), consteval (since C++20), inline, or static. 4) The body of the main function does not need to contain the return statement: if control reaches the end of main without encountering a return statement, the effect is that of executing return 0;. 5) Execution of the return (or the implicit return upon reaching the end of main) is equivalent to first leaving the function normally (which destroys the objects with automatic storage duration) and then calling std::exit with the same argument as the argument of the return. (std::exit then destroys static objects and terminates the program). 6) (since C++14) The return type of the main function cannot be deduced (auto main() {... is not allowed). 7) (since C++20) The main function cannot be a coroutine.
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/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } 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; }


It initializes the value current level, permutes the remaining values to the 'higher levels'. As the Assigning Action of the values reaches to the "Highest Level", it prints the permutation
This is a C++ Program code to check whether graph is DAG. In mathematics and computer science, a directed acyclic graph, is a directed graph with no directed cycles. It is formed by
Read the comments in the following program to understand each part of the program. This is a "default constructor" of the class, you do note that it's name is same as class name and
This is a sample program to illustrate the Bin-Packing algorithm using next fit heuristics. In the bin packing problem, objects of different volumes must be packed into a finite number