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adventofcode2024
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day 12 part 2

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magical 2024-12-12 05:42:20 +00:00
parent 1b49b24aa1
commit 54c84304aa
1 changed files with 26 additions and 0 deletions
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26
day12/sol.py
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@ -28,6 +28,7 @@ def solve(file):
done = set() # set of points which have been counted as part of a shape
total = 0
total2 = 0
for p in points():
if p in done: continue
shape = flood(p)
@ -38,8 +39,33 @@ def solve(file):
perim += 4-n
#print(get(p), area, perim)
total += area * perim
total2 += area * discount(shape)
print(total)
print(total2)
def discount(shape):
def sides(p):
x,y = p
s = 0
if (x+1,y) in shape: s += 1
if (x-1,y) in shape: s += 2
if (x,y+1) in shape: s += 4
if (x,y-1) in shape: s += 8
return s
# only count a side as free if the neighbor to the north or west
# does not have the same side free
perim = 0
for p in shape:
x,y = p
free = sides(p) ^ 15
if (x-1,y) in shape:
free &= sides((x-1,y))
if (x,y-1) in shape:
free &= sides((x,y-1))
perim += free.bit_count()
return perim
solve(open("sample4.in"))
solve(open("input"))