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Running
File size: 2,812 Bytes
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def parse_input(s):
# Convert the input string into alternating lengths of files and spaces
lengths = [int(c) for c in s]
# Convert to blocks representation
blocks = []
file_id = 0
pos = 0
for i, length in enumerate(lengths):
if i % 2 == 0: # File
blocks.extend([file_id] * length)
file_id += 1
else: # Space
blocks.extend([-1] * length) # -1 represents free space
return blocks
def calculate_checksum(blocks):
checksum = 0
for pos, block in enumerate(blocks):
if block != -1: # Skip free space
checksum += pos * block
return checksum
def compact_blocks_part1(blocks):
result = blocks.copy()
while True:
# Find rightmost file block
right = len(result) - 1
while right >= 0 and result[right] == -1:
right -= 1
if right < 0:
break
# Find leftmost free space
left = 0
while left < len(result) and result[left] != -1:
left += 1
if left >= right:
break
# Move one block
result[left] = result[right]
result[right] = -1
return result
def compact_blocks_part2(blocks):
result = blocks.copy()
# Get unique file IDs in descending order
file_ids = sorted(set(x for x in result if x != -1), reverse=True)
for file_id in file_ids:
# Find all blocks of this file
file_blocks = []
start = None
for i, block in enumerate(result):
if block == file_id:
if start is None:
start = i
file_blocks.append(block)
elif start is not None and block != file_id:
break
if not file_blocks:
continue
# Remove the file from its current position
for i in range(start, start + len(file_blocks)):
result[i] = -1
# Find leftmost position where file can fit
pos = 0
while pos < len(result):
if all(result[i] == -1 for i in range(pos, pos + len(file_blocks)) if i < len(result)):
# Place file here
for i in range(len(file_blocks)):
result[pos + i] = file_id
break
pos += 1
return result
# Read input
with open("input.txt", "r") as f:
input_data = f.read().strip()
# Part 1
blocks = parse_input(input_data)
compacted = compact_blocks_part1(blocks)
checksum = calculate_checksum(compacted)
print(str(checksum))
# Part 2
blocks = parse_input(input_data)
compacted = compact_blocks_part2(blocks)
checksum = calculate_checksum(compacted)
print(str(checksum)) |