What is really happening in this code?

Question

I have a code which includes a recursive function. I have wasted a lot of time on recursion but I still couldn\'t get it really:

#include
void         


        

Answer 1

next time it calls itself it has a smaller value

count(int m)
{
 if(m>0)
 count(m-1); // now it is calling the method "count" again, except m is one less
 printf("%d",m);
}

So first it will call count with 10, then it will call it with 9, then 8, then 7..... all the way until this if statement isn't true:

if(m>0)

What might be confusing you is the if statement only applies to the next line (printf isn't part of the if statement)

so you have:

count(int m)
    {
     if(m>0)
     {
         count(m-1); // now it is calling the method "count" again, except m is one less
     }
     printf("%d",m);
    }

So, the recursive calls will stop once m is not > 0, and then it will call the printf.

After it calls printf for when m is 0, then it will return from that 'count' call, (Back to where m was equal to 1), and then it will call the printf when m is 1, and then when m is 2, .....

So the output should be:

"0 1 2 3 4 5 6 7 8 9 10"

EDIT: In terms of a stack:

This is what the stack is doing:

count(10) // push count(10)

->

count(9) // push count(9)
count (10)

->

...

->

count(0) // push count(0)
count(1)
count(2)
count(3)
count(4)
count(5)
count(6)
count(7)
count(8)
count(9)
count(10)

-> (and then it starts printing and popping the method off the stack)

// pop count(0), and printf(0)
count(1)
count(2)
count(3)
count(4)
count(5)
count(6)
count(7)
count(8)
count(9)
count(10)

->

// pop count(1), and printf(1)
count(2)
count(3)
count(4)
count(5)
count(6)
count(7)
count(8)
count(9)
count(10)

->

...

->

// pop count(9), and printf(9)
count(10)

->

// pop count(10), and printf(10)