136 lines
3.7 KiB
Python
136 lines
3.7 KiB
Python
|
"""
|
|||
|
|
--- Part Two ---
|
|||
|
|
|
|||
|
|
As you watch the crane operator expertly rearrange the crates, you
|
|||
|
|
notice the process isn't following your prediction.
|
|||
|
|
|
|||
|
|
Some mud was covering the writing on the side of the crane, and you
|
|||
|
|
quickly wipe it away. The crane isn't a CrateMover 9000 - it's a
|
|||
|
|
CrateMover 9001.
|
|||
|
|
|
|||
|
|
The CrateMover 9001 is notable for many new and exciting features: air
|
|||
|
|
conditioning, leather seats, an extra cup holder, and the ability to
|
|||
|
|
pick up and move multiple crates at once.
|
|||
|
|
|
|||
|
|
Again considering the example above, the crates begin in the same
|
|||
|
|
configuration:
|
|||
|
|
|
|||
|
|
[D]
|
|||
|
|
[N] [C]
|
|||
|
|
[Z] [M] [P]
|
|||
|
|
1 2 3
|
|||
|
|
|
|||
|
|
Moving a single crate from stack 2 to stack 1 behaves the same as
|
|||
|
|
before:
|
|||
|
|
|
|||
|
|
[D]
|
|||
|
|
[N] [C]
|
|||
|
|
[Z] [M] [P]
|
|||
|
|
1 2 3
|
|||
|
|
|
|||
|
|
However, the action of moving three crates from stack 1 to stack 3
|
|||
|
|
means that those three moved crates stay in the same order, resulting
|
|||
|
|
in this new configuration:
|
|||
|
|
|
|||
|
|
[D]
|
|||
|
|
[N]
|
|||
|
|
[C] [Z]
|
|||
|
|
[M] [P]
|
|||
|
|
1 2 3
|
|||
|
|
|
|||
|
|
Next, as both crates are moved from stack 2 to stack 1, they retain
|
|||
|
|
their order as well:
|
|||
|
|
|
|||
|
|
[D]
|
|||
|
|
[N]
|
|||
|
|
[C] [Z]
|
|||
|
|
[M] [P]
|
|||
|
|
1 2 3
|
|||
|
|
|
|||
|
|
Finally, a single crate is still moved from stack 1 to stack 2, but now
|
|||
|
|
it's crate C that gets moved:
|
|||
|
|
|
|||
|
|
[D]
|
|||
|
|
[N]
|
|||
|
|
[Z]
|
|||
|
|
[M] [C] [P]
|
|||
|
|
1 2 3
|
|||
|
|
|
|||
|
|
In this example, the CrateMover 9001 has put the crates in a totally
|
|||
|
|
different order: MCD.
|
|||
|
|
|
|||
|
|
Before the rearrangement process finishes, update your simulation so
|
|||
|
|
that the Elves know where they should stand to be ready to unload the
|
|||
|
|
final supplies. After the rearrangement procedure completes, what crate
|
|||
|
|
ends up on top of each stack?
|
|||
|
|
"""
|
|||
|
|
import re
|
|||
|
|
import string
|
|||
|
|
|
|||
|
|
|
|||
|
|
def main():
|
|||
|
|
stacks = []
|
|||
|
|
|
|||
|
|
with open("input.txt", "r", encoding="utf-8") as f:
|
|||
|
|
# First, create the stacks.
|
|||
|
|
for line in f:
|
|||
|
|
if "[" in line and "]" in line:
|
|||
|
|
# A sample line could be:
|
|||
|
|
#
|
|||
|
|
# [Z] [M] [P]
|
|||
|
|
#
|
|||
|
|
# And we’re interested in the letters, meaning we need
|
|||
|
|
# the following indexes:
|
|||
|
|
#
|
|||
|
|
# [Z] [M] [P]
|
|||
|
|
# 1 5 9
|
|||
|
|
for i in range(1, 9999, 4):
|
|||
|
|
try:
|
|||
|
|
char = line[i]
|
|||
|
|
except IndexError:
|
|||
|
|
continue
|
|||
|
|
if char not in string.ascii_letters:
|
|||
|
|
continue
|
|||
|
|
|
|||
|
|
stack_index = int(((i - 1) / 4))
|
|||
|
|
while len(stacks) <= stack_index:
|
|||
|
|
stacks.append([])
|
|||
|
|
|
|||
|
|
stacks[stack_index].append(char)
|
|||
|
|
|
|||
|
|
# Stacks are loaded top to bottom from the input file, meaning
|
|||
|
|
# the lowest character is now the last entry of each array. To
|
|||
|
|
# be able to ``pop()`` the top crates off the stacks, we need
|
|||
|
|
# the highest characters last in our arrays, so we reverse them.
|
|||
|
|
for i, stack in enumerate(stacks):
|
|||
|
|
stack.reverse()
|
|||
|
|
stacks[i] = stack
|
|||
|
|
|
|||
|
|
# Now we need to replicate the movements described in the input
|
|||
|
|
# file.
|
|||
|
|
regex = re.compile(r"move (\d+) from (\d+) to (\d+)")
|
|||
|
|
f.seek(0)
|
|||
|
|
for line in f:
|
|||
|
|
match = regex.match(line)
|
|||
|
|
if match:
|
|||
|
|
amount = int(match[1])
|
|||
|
|
source_stack = int(match[2]) - 1
|
|||
|
|
target_stack = int(match[3]) - 1
|
|||
|
|
|
|||
|
|
print(f"Moving {amount} crates from {source_stack} to {target_stack}")
|
|||
|
|
|
|||
|
|
pickup_index = amount * -1
|
|||
|
|
stacks[target_stack].extend(stacks[source_stack][pickup_index:])
|
|||
|
|
stacks[source_stack] = stacks[source_stack][:pickup_index]
|
|||
|
|
|
|||
|
|
answer = ""
|
|||
|
|
for stack in stacks:
|
|||
|
|
if len(stack):
|
|||
|
|
answer += stack.pop()
|
|||
|
|
|
|||
|
|
print(f"The top crates are {answer}")
|
|||
|
|
|
|||
|
|
|
|||
|
|
if __name__ == "__main__":
|
|||
|
|
main()
|