def part_one(filename: str) -> int:
public_keys = read_integers(get_path(__file__, filename))
pub_key1, pub_key2 = public_keys[0], public_keys[1]
loop1, loop2 = get_loop_size(pub_key1), get_loop_size(pub_key2)
encryption_key = transform(pub_key1, loop2)
assert (encryption_key == transform(pub_key2, loop1))
return encryption_key
def part_two(filename: str) -> int:
ints = read_integers(get_path(__file__, filename))
# use twosum solution from p1 to reduce time complexity from
# O(n^3) to O(n^2)
for i, n in enumerate(ints):
multiplier = two_sum(ints[i + 1:], 2020 - n)
if multiplier != -1:
return n * multiplier
return -1
def part_one(filename: str) -> int:
ints = read_integers(get_path(__file__, filename))
ints.sort()
ones, threes, v = 0, 0, 0
for x in ints:
threes += (x - v == 3)
ones += (x - v == 1)
v = x
return ones * (threes + 1)
def part_two_2(filename: str) -> int:
ints = read_integers(get_path(__file__, filename))
ints_set = set(ints)
ints.sort()
ways = [0] * (max(ints) + 1)
for x in [1, 2, 3]:
ways[x] = int(x in ints)
for i in range(2, max(ints) + 1):
if i in ints_set:
ways[i] += ways[i - 1] + ways[i - 2] + ways[i - 3]
return ways[-1]
def part_two_1(filename: str) -> int:
ints = read_integers(get_path(__file__, filename))
ints_set = set(ints)
cache = [-1] * max(ints)
def number_ways(v):
if v not in ints_set:
return 0
if v == max(ints):
return 1
if cache[v] == -1:
cache[v] = sum([number_ways(v + x) for x in range(1, 4)])
return cache[v]
return sum([number_ways(x) for x in range(1, 4)])
def part_one(filename: str) -> int:
ints = read_integers(get_path(__file__, filename))
return two_sum(ints, 2020)
def part_one(filename: str, preamble: int) -> int:
ints = read_integers(get_path(__file__, filename))
for i in range(preamble, len(ints)):
if not can_sum(ints[i], ints[i - preamble:i + 1]):
return ints[i]
return -1
def part_two(filename: str, preamble: int) -> int:
ints = read_integers(get_path(__file__, filename))
n = part_one(filename, preamble)
return sub_array_sum(n, ints)