euler/python/e077.py
2019-08-16 17:14:33 -04:00

45 lines
998 B
Python

from lib_prime import primes
from functools import lru_cache
def euler_077():
def get_prime_sequence_dict(n_max):
""" Returns a dict that maps a
current prime to the following prime. """
ps = primes(n_max)
ps_current = ps[0]
ps_dict = {}
for p in ps[1:]:
ps_dict[ps_current] = p
ps_current = p
return ps_dict
prime_dict = get_prime_sequence_dict(10000)
@lru_cache(maxsize=1000000)
def possible_sums(n, n_orig, d):
if d == n_orig:
return 0
if n == 0:
return 1
if n < 0:
return 0
if d > n:
return 0
s_1 = possible_sums(n - d, n_orig, d)
s_2 = possible_sums(n, n_orig, prime_dict[d])
return s_1 + s_2
for n in range(1000):
if possible_sums(n, n, 2) > 5000:
return n
if __name__ == "__main__":
print("e077.py: " + str(euler_077()))
assert(euler_077() == 71)