Recursive Function Exercise

What I wrote last is how to solve problems about recursive function.  In this week, I will write some exercises about recursive function.

count_elements(‘snork’)

count_elements([2, 1, 3])

The answer for the first one is 1, because ‘snork’ is not a list.  For the second one, the answer is 1.  Since [2, 1, 3] is a list, the function will run sum([count_elements(x) for x in L]) and will return sum([1 ,1, 1]) which is 3.

nd(‘ox’)

nd([])

The answer for the first one is 0, because ‘ox’ is not a list.  For the second one, since [] is a list though it is an empty list, the function will run 1 + max([nd(x) for x in (L+ [‘ox'])]) and L will become ['ox'].  Since 'ox' is not a list, which will let L become [0].  Then the function will return 1 eventually.

After doing these exercises, solving recursive function becomes much easier.