[Norbi34]

Can someone explain me how this function returns 164618 for f(17).

void f(int x)
{
   if(x>3)
   {
       cout<<x-1;
       f(x/3);
       cout<<x+1;
   }
}

[gurlhackerclub]

interesting, I do notice there is no new line character or space separator.

So the function outputs, x -1, which is 17 -1
16

Then the function calls itself with 17 divided by 3. This will be 5.
So you get 5 - 1 = 4 and 5+1 = 6

Then the function adds 1 to x and outputs
18

The output would be much easier to read if you added a new line or space.
example
cout<<x-1<< " ";
16 4 6 18

[SIM-3991524]

Its just the way you were using cout in f() that made it confusing

Try this example, should make a little more sense
Spoiler (Click to View)

Code

#include <iostream>

using namespace std;

void f(int x, int nth_iteration)
{
   cout << nth_iteration << "\t" << x << endl;
   if (x > 3)
   {
       f(x / 3, nth_iteration + 1);
   }
}

int main()
{
   f(12500, 1);
   int done; cin >> done;
}

Example output
Spoiler (Click to View)

Code

1       12500
2       4166
3       1388
4       462
5       154
6       51
7       17
8       5
9       1

All f() does is divide a number by 3 until it is less than 3

[saltycracker]

To understand recursion, you have to understand a function call. If you understand the basic mechanics of a function call then recursion is simply a function which calls itself.

Note: The topic of recursion(function recursion and recursive data structures) can get involved and very complicated but at its simplest, its really just a function call.