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2024 day 9 part 2

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Thibaud Gasser 2024-12-23 15:58:09 +01:00
parent d7b0cce606
commit 14426b0697
1 changed files with 41 additions and 24 deletions
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65
2024/day9/day9.py
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@ -29,10 +29,8 @@ def parse_disk(data):
return disk, disk2 return disk, disk2
def main(inp): def part1(disk):
disk, disk2 = parse_disk(inp)
max_file_location = max(disk.keys()) max_file_location = max(disk.keys())
write_ptr = 0 write_ptr = 0
read_ptr = max_file_location read_ptr = max_file_location
while True: while True:
@ -47,47 +45,66 @@ def main(inp):
disk[write_ptr] = disk[read_ptr] disk[write_ptr] = disk[read_ptr]
del disk[read_ptr] del disk[read_ptr]
checksum = sum(i * disk.get(i, 0) for i in range(max_file_location)) checksum = sum(i * disk.get(i, 0) for i in range(max_file_location))
print("Part 1: ", checksum) return checksum
print(len(disk2))
write_ptr = 0 def part2(disk):
read_ptr = len(disk2) - 1 max_id = max(f.id_ for f in disk)
for file_index in range(len(disk2) - 1, 0, -1): for i in range(max_id, -1, -1):
file = disk2[file_index] file, file_index = next((file, index) for index, file in enumerate(disk) if file.id_ == i)
if file.kind != "file":
continue
# find index of the first gap large enough # find index of the first gap large enough
free_index, free_space = next(((i, b) for i, b in enumerate(disk2) if b.kind == "free" and b.size >= file.size), (None, None)) free_index, free_space = next(((i, b) for i, b in enumerate(disk) if b.kind == "free" and b.size >= file.size), (None, None))
if free_index is None: if free_index is None:
continue continue
# add a free space in place of the file if free_index >= file_index: # always move file to the left
disk2[file_index] = Item("free", file.size) continue
# insert file just before free space
disk2.insert(free_index, file)
# decrease free space by file size (in case free space is larger) # decrease free space by file size (in case free space is larger)
free_space.size -= file.size disk[free_index].size -= file.size
# add a free space in place of the file
disk[file_index] = Item("free", file.size)
# insert file just before free space
disk.insert(free_index, file)
#debug = debug_print(disk)
#print(debug)
# calculate checksum for part2
total_checksum = 0 total_checksum = 0
offset = 0 offset = 0
print(disk2) #print(disk)
print(len(disk2)) debug_print(disk)
for f in disk2: #print(len(disk))
for f in disk:
if f.kind != "file": if f.kind != "file":
offset += f.size offset += f.size
continue continue
# S(n) = n*(n+1) // 2 # S(n) = n*(n+1) // 2
print(f"checksum = {f.id_} * ({offset} * {f.size} + ({f.size} * ({f.size - 1})) // 2") #print(f"checksum = {f.id_} * ({offset} * {f.size} + ({f.size} * ({f.size - 1})) // 2")
checksum = f.id_ * (offset * f.size + (f.size * (f.size - 1)) // 2) checksum = f.id_ * (offset * f.size + (f.size * (f.size - 1)) // 2)
print(f, checksum) #print(f, checksum, total_checksum)
offset += f.size offset += f.size
total_checksum += checksum total_checksum += checksum
print(total_checksum) return total_checksum
def main(inp):
disk, disk2 = parse_disk(inp)
print("Part 1: ", part1(disk))
print("Part 2: ", part2(disk2))
def debug_print(disk):
res = []
for item in disk:
if item.kind == "free" and item.size > 0:
res.extend(["."] * item.size)
else:
res.extend([str(item.id_)] * item.size)
return "".join(res)