Question

i have a function called fun1(), which is used for recursion. I am confused regarding the first call to this fun(--n);. What it will do and how will my stack pop my functions after each function finishes?

void fun(int n)
{
    if(n>0)
    {
        fun(--n);
        printf("%d",n);
        fun(--n);
    }
}

My main function is as below:

    int a;
    a=3;
    fun(a);

I want to know the order of execution and what my stack will contain before, during, and after the function call of the first fun(--n).

Answer 1

Your output will be 0, then 1, then 2, and then 0.

1. Initially called with 3
2. Greater than 0, it calls fun(–n), which makes it 2.
3. This continues until it reaches 0.
4. It continues to the printf(), and prints 0 to the console.

What you aren’t seeing is the intermediate calls. This is the full output (before the n > 0 part):

Fun call before n > 0; n = 3
Fun call before n > 0; n = 2
Fun call before n > 0; n = 1
Fun call before n > 0; n = 0
0
Fun call before n > 0; n = -1
1
Fun call before n > 0; n = 0
2
Fun call before n > 0; n = 1
Fun call before n > 0; n = 0
0
Fun call before n > 0; n = -1