Python/project_euler/problem_10/sol3.py
Du Yuanchao 4d0a8f2355
Optimized recursive_bubble_sort (#2410)
* optimized recursive_bubble_sort

* Fixed doctest error due whitespace

* reduce loop times for optimization

* fixup! Format Python code with psf/black push

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
2020-09-10 10:31:26 +02:00

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"""
https://projecteuler.net/problem=10
Problem Statement:
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million using Sieve_of_Eratosthenes:
The sieve of Eratosthenes is one of the most efficient ways to find all primes
smaller than n when n is smaller than 10 million. Only for positive numbers.
"""
def prime_sum(n: int) -> int:
"""Returns the sum of all the primes below n.
>>> prime_sum(2_000_000)
142913828922
>>> prime_sum(1_000)
76127
>>> prime_sum(5_000)
1548136
>>> prime_sum(10_000)
5736396
>>> prime_sum(7)
10
>>> prime_sum(7.1) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
TypeError: 'float' object cannot be interpreted as an integer
>>> prime_sum(-7) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
IndexError: list assignment index out of range
>>> prime_sum("seven") # doctest: +ELLIPSIS
Traceback (most recent call last):
...
TypeError: can only concatenate str (not "int") to str
"""
list_ = [0 for i in range(n + 1)]
list_[0] = 1
list_[1] = 1
for i in range(2, int(n ** 0.5) + 1):
if list_[i] == 0:
for j in range(i * i, n + 1, i):
list_[j] = 1
s = 0
for i in range(n):
if list_[i] == 0:
s += i
return s
if __name__ == "__main__":
# import doctest
# doctest.testmod()
print(prime_sum(int(input().strip())))