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

1,2,3,4,5,6
1,2,3,4,5,6

1,2,3
1,2,3

1,4
1,4

4,5,6

Answer 1

In the context of a recursive factorial function, the backward phase refers to the phase where the results of the recursive calls are combined to produce the final output after the base case has been reached.

Here's the breakdown of the provided output:

1. `factorial(3)` - This is where the factorial function starts executing, calling `factorial(3)`. This is part of the forward phase.
2. `3 * factorial(2)` - Still part of the forward phase, as we're still making recursive calls.
3. `3 * 2 * factorial(1)` - Continuing the forward phase with recursive calls.
4. `3 * 2 * 1` - This reflects the moment when we have reached the base case, and we are starting the backward phase.
5. `3 * 2` - This is part of the backward phase, as we are resolving the earlier multiplication.
6. `6` - The final result of the factorial calculation, which is also part of the backward phase.

Given this explanation, the lines of output that reflect the backward phase are:

**4, 5, 6**

Thus, the correct response is:

**4,5,6**