Advent of Code :: Problem 10

problem10.py

adapters = np.sort(adapters)
start = 0
end = np.max(adapters) + 3

cache = {}

def next_in_line(last_link):
    if last_link in cache:
        return cache[last_link]

    if end - last_link <= 3:
        cache[last_link] = 1
        return 1

    # Which adapters can I use next?
    D = adapters - last_link
    candidates = adapters[np.where((0 < D) & (D <= 3))[0]]

    S = 0
    for c in candidates:
        S = S + next_in_line(c)

    cache[last_link] = S
    return S

print(next_in_line(start))