Question

For the recursive factorial function output shown below, which lines of output would reflect the backward phase?

1 factorial(3)
2 3 * factorial(2)
3 3 * 2 * factorial(1)
4 3 * 2 * 1
5 3 * 2
6 6
(1 point)
Responses

1,4
1,4

1,2,3
1,2,3

4,5,6
4,5,6

1,2,3,4,5,6

Answer 1

In a recursive factorial function, the backward phase occurs after all the recursive calls have been made and is where the results of those calls are combined to produce the final output.

Looking at the lines:

1. `factorial(3)` - Initiating the call.
2. `3 * factorial(2)` - During the first level of recursion.
3. `3 * 2 * factorial(1)` - Continuing recursion.
4. `3 * 2 * 1` - The base case `factorial(1)` has been resolved.
5. `3 * 2` - The result of `factorial(2)` is combined with `3`.
6. `6` - The final result of `factorial(3)`.

The backward phase starts when the base case is reached (line 4) and continues until the final result is computed (line 6). Therefore, the lines that reflect the backward phase are:

4, 5, 6

So, the correct response is:

**4,5,6**