C++ Programming Code Examples
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Slice a valarray
/* Slice a valarray */
#include <iostream>
#include <valarray>
#include <cmath>
using namespace std;
int main()
{
valarray<int> v(10);
for(int i=0; i<10; i++)
v[i] = i;
cout << "Original contents: ";
for(int i=0; i<10; i++)
cout << v[i] << " \n\n";
valarray<int> result = v[slice(0,5,2)];
cout << "Contents of result: ";
for(int i=0; i<result.size(); i++)
cout << result[i] << " ";
cout << endl;
}
/*
Original contents: 0
1
2
3
4
5
6
7
8
9
Contents of result: 0 2 4 6 8
*/
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.
Valarray class. A valarray object is designed to hold an array of values, and easily perform mathematical operations on them. It also allows special mechanisms to refer to subsets of elements in the arrays (see its operator[] overload). Most mathematical operations can be applied directly to valarray objects, including arithmetical and comparison operators, affecting all its elements. The valarray specification allows for libraries to implement it with several efficiency optimizations, such as parallelization of certain operations, memory recycling or support for copy-on-reference / copy-on-write optimizations. Implementations may even replace valarray as the return type for standard functions described below, provided they behave as, and can be converted to, valarray objects.
Return size. Returns the number of elements in the valarray. The C++ valarray::size function returns the size of the valarray. The size() function is defined in valarray header file. This function is used to find the size of valarray and returns the size of valarray. This function doesn't takes any parameter. Function returns the number of elements in the valarray.
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.
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.
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. 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.
Arithmetic Operator is used to performing mathematical operations such as addition, subtraction, multiplication, division, modulus, etc., on the given operands. For example: 6 + 3 = 9, 5 - 3 = 2, 3 * 4 = 12, etc. are the examples of arithmetic operators. Let's discuss the different types of Arithmetic Operators in the C programming. Plus Operator is a simple Plus (+) Operator used to add two given operands. We can use Plus Operator with different data types such as integer, float, long, double, enumerated and string type data to add the given operand. The minus operator is denoted by the minus (-) symbol. It is used to return the subtraction of the first number from the second number. The data type of the given number can be different types, such as int, float, double, long double, etc., in the programing 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.
#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.
Problem takes E edges as input and outputs vertex cover of the graph, implementing the following heuristic. There is no "Polynomial" time algorithm "invented up to date" to find
