# Recursion

**Recursion**is derived from the word recur which means repetition

There are two basic requirement for recursion:

i) The function must call itself again and again

ii) The function must have an exit condition.

When to use recursion:

Recursion can be used for any function involving loop i.e, all loops can be converted into recursion

- A recursion procedure or function is one that repeats itself through calls made on it.
- Repeat calls are terminated as soon as certain condition is satisfied.
- Every recursive function must contain a way to get out of the recursive process
- Recursive process is complex and involved
- Recursive function may be defined as a repeated iteration , which calls itself until a certain condition is met.

**Eg:**

void recurse ()

{

recurse (); //Function call itself

}

int main ()

{

recurse (); // set off recursion

return();

}

**Example of Recursion**

/* Sum of N nos. through recursion */

# include <iostream.h>

int add (int x);

main()

{

int n;

cout<<"Enter any positive no. \n";

cin>>n;

cout<<"The sum of first"<<n<<"integer="<<add(n)<<endl;

return 0;

}

int add (int n)

{

if (n==0)

return 0;

else return[n+add(n-1)]

}

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