mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-30 16:31:08 +00:00
98e9d6bdb6
* 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
54 lines
1.4 KiB
Python
54 lines
1.4 KiB
Python
"""
|
||
Project Euler Problem 4: https://projecteuler.net/problem=4
|
||
|
||
Largest palindrome product
|
||
|
||
A palindromic number reads the same both ways. The largest palindrome made
|
||
from the product of two 2-digit numbers is 9009 = 91 × 99.
|
||
|
||
Find the largest palindrome made from the product of two 3-digit numbers.
|
||
|
||
References:
|
||
- https://en.wikipedia.org/wiki/Palindromic_number
|
||
"""
|
||
|
||
|
||
def solution(n: int = 998001) -> int:
|
||
"""
|
||
Returns the largest palindrome made from the product of two 3-digit
|
||
numbers which is less than n.
|
||
|
||
>>> solution(20000)
|
||
19591
|
||
>>> solution(30000)
|
||
29992
|
||
>>> solution(40000)
|
||
39893
|
||
>>> solution(10000)
|
||
Traceback (most recent call last):
|
||
...
|
||
ValueError: That number is larger than our acceptable range.
|
||
"""
|
||
|
||
# fetches the next number
|
||
for number in range(n - 1, 9999, -1):
|
||
|
||
str_number = str(number)
|
||
|
||
# checks whether 'str_number' is a palindrome.
|
||
if str_number == str_number[::-1]:
|
||
|
||
divisor = 999
|
||
|
||
# if 'number' is a product of two 3-digit numbers
|
||
# then number is the answer otherwise fetch next number.
|
||
while divisor != 99:
|
||
if (number % divisor == 0) and (len(str(number // divisor)) == 3.0):
|
||
return number
|
||
divisor -= 1
|
||
raise ValueError("That number is larger than our acceptable range.")
|
||
|
||
|
||
if __name__ == "__main__":
|
||
print(f"{solution() = }")
|