Explanation

Question

Hello everyone,
Can someone please explain this piece of code for me.
I thought the output was 16, but its 19. I just cant figure out why its 19. Can anyone explain why its 19?
def test(i,j):
If i == 0:
return j
else:
return test(i-1, i+j)
print(test(4,9))

Answer 1

Work your way down.
test(4, 9) # (4, 9)
== test(4-1, 4+9) # (3, 13)
== test(3-1, 13+3) # (2, 16)
== test(2-1, 16+2) # (1, 18)
== test(1-1, 18+1) # (0, 19)
== 19.