Practice 6: Recursion

This practice problems set will guide you through recursion in programming.

Some problems shall be approached with recursion only. Direct approach is not allowed. Loop is also not allowed.

1. Factorial Function factorial(n)
2. Power Function pow(x, n) computing x ** n.
3. Sum of a list sum_list(x) computing sum of every element in the list.
4. Reversing a string reverse_string(s).
5. Sum up from 0 to n sum_up(n).
6. Finding string length str_len(s).
7. Counting down from n to 0 count_down(n).
8. Nested List Sum nested_sum(x) computing sum of every element in a nested list. For example, nested_sum([1, [2, [3, 4], 5], 6]) shall yield 21.

In Python, how to check whether the variable is type int, float, str, list, or etc.

x = 'Hello'
isinstance(x, str)  # True
isinstance(x, int)  # False

y = '50'
isinstance(y, str)  # True
isinstance(y, int)  # False