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What do show_up(3) and show_down(3) print? Say it before you run it.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
What do show_up(3) and show_down(3) print? Say it before you run it.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. A line before the recursive call runs on the way down. A line after it runs on the way back up.
- In
show_up, theprintis after the call. The callshow_up(3)has to wait forshow_up(2), which waits forshow_up(1), which waits forshow_up(0), the base case. Then the answers come back:print(1), thenprint(2), thenprint(3). The output is 1, 2, 3. - In
show_down, theprintis before the call. So 3 is shown first, then the call toshow_down(2), and so on. The output is 3, 2, 1.
Check. Run it. The first three lines are 1, 2, 3, and the next three are 3, 2, 1.
Answer: 1 2 3 and then 3 2 1, each number on its own line.
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