How to Reverse a Number into a List Using Recursion in Python

Question: Convert a number into a reversed list of its digits, e.g., 1234 → [4,3,2,1], using recursion.

Simple method: cast the integer to a string, reverse it, and convert each character back to an integer.

Standard recursion

def reverse_order_list1(lst:list, tmp=[]):
    if len(lst) == 0:
        return tmp
    num = lst.pop()
    tmp.append(int(num))
    return reverse_order_list1(lst, tmp=tmp)
print(reverse_order_list1(list(str(1234))))

Tail recursion

def reverse_order_list2(lst:list, tmp=[]):
    if len(lst) > 0:
        num = lst.pop()
        tmp.append(int(num))
        reverse_order_list2(lst, tmp=tmp)
    return tmp
print(reverse_order_list2(list(str(1234))))

Note: In Python, recursion is generally discouraged for such tasks because loops are more efficient, but recursion can be convenient in certain scenarios.