# C++ Programming Code Examples

## C++ > Recursion Code Examples

### program to Find Sum of Natural Numbers using Recursion

/* program to Find Sum of Natural Numbers using Recursion Example to find the sum of natural numbers by using a recursive function. The positive numbers 1, 2, 3... are known as natural numbers. The program below takes a positive integer from the user and calculates the sum up to the given number. You can find the sum of natural numbers using loops as well. However, you will learn to solve this problem using recursion here In this program, the number entered by the user is passed to the add() function. Suppose, 10 is entered by the user. Now, 10 is passed to the add() function. This function adds 10 to the addition result of 9 (10 - 1 = 9). Next time, 9 is added to the addition result of 8 (9 - 1 = 8). This goes on until the number reaches 0, when the function returns 0. Now, every function is returned to calculate the end result: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55. */ #include<iostream> using namespace std; int add(int n); int main() { int n; cout << "Enter a positive integer: "; cin >> n; cout << "Sum = " << add(n); return 0; } int add(int n) { if(n != 0) return n + add(n - 1); return 0; }

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.

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.

#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.

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.

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.

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.

The cin object is used to accept input from the standard input device i.e. keyboard. It is defined in the iostream header file. C++ cin statement is the instance of the class istream and is used to read input from the standard input device which is usually a keyboard. The extraction operator(>>) is used along with the object cin for reading inputs. The extraction operator extracts the data from the object cin which is entered using the keyboard. The "c" in cin refers to "character" and "in" means "input". Hence cin means "character input". The cin object is used along with the extraction operator >> in order to receive a stream of characters.

C++ Language code to compute the area of a triangle using determinants. The 'plus/minus' in this case is meant to take whichever sign is needed so the 'answer is positive'. Do not say

Merge-Sort is based on an algorithmic design pattern called Divide & Conquer. It forms tree structure. The height of the tree will be log(n) And we merge n element at every level of the

Function to check if "tree is empty". Function to count number of "nodes recursively". And function to search for an element. Function to search for an element recursively. Function

Function returns true if the number passed to the function is a 'prime number', returns false if the number passed is not a 'prime number'. The appropriate message is printed from the