euler/python/e050.py

from lib_prime import primes


def find_max_series(start_index, series_list, series_set):
    """ Start at the given index and sum up consecutive primes
    into total. If a total is in the series_set (i.e. a prime) then
    store the current number of consecutive primes (length) and the total.
    If the total exceeds the last value of the given primes no longer
    sequence can be found. Return the max sequence length and total. """
    series_max = series_list[-1]
    total_max = 0
    total = 0
    for i in range(start_index, len(series_list)):
        total = total + series_list[i]
        if total in series_set:
            length = i - start_index + 1
            total_max = total
        if total > series_max:
            return (length, total_max)


def euler_050():
    n_max = 1000000
    ps = primes(n_max)
    ps_set = set(ps)
    s = max([x for x in [find_max_series(i, ps, ps_set)
                         for i in range(0, len(ps))] if x])
    return s[1]


if __name__ == "__main__":
    print("e050.py: " + str(euler_050()))
    assert(euler_050() == 997651)