project_euler/problem_10

project_euler/problem_10/sol3.py

@@ -0,0 +1,58 @@
+"""
+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())))