Python/project_euler/problem_001/sol2.py
Michael D 98e9d6bdb6
Fix style of the first ten solutions for Project Euler (#3242)
* Fix style of the first ten solutions for Project Euler

- Unify the header docstring, and add reference URLs to wikipedia
  or similar
- Fix docstrings to be properly multilined
- Add newlines where appropriate
- Add doctests where they were missing
- Remove doctests that test for the correct solution
- fix obvious spelling or grammar mistakes in comments and
  exception messages
- Fix line endings to be UNIX. This makes two of the files seem
  to have changed completely
- no functional changes in any of the solutions were done
  (except for the spelling fixes mentioned above)

* Fix docstrings and main function as per Style Guide
2020-10-25 08:53:16 +05:30

39 lines
851 B
Python

"""
Project Euler Problem 1: https://projecteuler.net/problem=1
Multiples of 3 and 5
If we list all the natural numbers below 10 that are multiples of 3 or 5,
we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.
"""
def solution(n: int = 1000) -> int:
"""
Returns the sum of all the multiples of 3 or 5 below n.
>>> solution(3)
0
>>> solution(4)
3
>>> solution(10)
23
>>> solution(600)
83700
"""
total = 0
terms = (n - 1) // 3
total += ((terms) * (6 + (terms - 1) * 3)) // 2 # total of an A.P.
terms = (n - 1) // 5
total += ((terms) * (10 + (terms - 1) * 5)) // 2
terms = (n - 1) // 15
total -= ((terms) * (30 + (terms - 1) * 15)) // 2
return total
if __name__ == "__main__":
print(f"{solution() = }")