### Comment on

 Need Help??

Hello all! I have never completely understood recursion. I have some understanding of what happens when you have one simple recursive call in a subroutine like the following:

```sub factorial
{
factorial
my (\$n) = @_;
return 1 if \$n == 0;
return factorial(\$n-1) * \$n;
}

The sub factorial is called again and again until \$n is equal to 0. Then the 1 is returned and all the past calls are then 'really' executed in reverse order, producing the factorial of the number \$n.

OK. But I do not understand how recursion works when there is more than 1 recursive call in a subroutine, like the following:

```sub hanoi
{
my (\$n, \$start, \$end, \$extra) = @_;
if (\$n == 1)
{
print "Move disk #1 from \$start to \$end.\n";
}
else
{
hanoi(\$n-1, \$start, \$extra, \$end);
print "Move disk #\$n from \$start to \$end.\n";
hanoi(\$n-1, \$extra, \$end, \$start);
}
}

The output will be:

```Move disk #1 from A to C.
Move disk #2 from A to B.
Move disk #1 from C to B.
Move disk #3 from A to C.
Move disk #1 from B to A.
Move disk #2 from B to C.
Move disk #1 from A to C.

Can anyone explain precisely why this is the output. If the first recursive call were called over and over untill \$n==1 and then they 'fell' back and all the calls were executed in reverse order, the third line of output does not make sense. Is the next recursive line then executed? A step-by-step explanation is what I am looking for.

Thank you!

In reply to Recursion Confusion by live4tech

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