Good morning! Here's our prompt for today.
We're provided a positive integer num. Can you write a method to repeatedly add all of its digits until the result has only one digit?
Here's an example: if the input was 49, we'd go through the following steps:
SNIPPET
1// start with 49
24 + 9 = 13
3
4// since the previous addition was 13,
5// move onto summing 13's digits
61 + 3 = 4We would then return 4.
Constraints
- Input will be in the range between
0and1000000000 - Expected time complexity :
O(log n) - Expected space complexity :
O(1)
Try to solve this here or in Interactive Mode.
How do I practice this challenge?
xxxxxxxxxx29
import functools​​def sum_digits(num): # fill in return num​​import unittest​​class Test(unittest.TestCase): def test_1(self): assert sum_digits(1) == 1 print("PASSED: `sum_digits(1)` should return `1`")​ def test_2(self): assert sum_digits(49) == 4 print("PASSED: `sum_digits(49)` should return `4`")​ def test_3(self): assert sum_digits(439230) == 3 print("PASSED: `sum_digits(439230)` should return `3`")​​if __name__ == "__main__": unittest.main(verbosity=2) print("Nice job, 3/3 tests passed!")​OUTPUT
:001 > Cmd/Ctrl-Enter to run, Cmd/Ctrl-/ to comment
Here's how we would solve this problem...
How do I use this guide?
Access all course materials today
The rest of this tutorial's contents are only available for premium members. Please explore your options at the link below.