advent-of-code/2021/09/prog.py

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2023-08-02 11:46:44 +02:00
import math
VERBOSE = True
def verbose(s = "", *args, **kwargs):
if VERBOSE:
print(s, *args, **kwargs)
def get_input(sample = False, part = 1):
with open(f'sample_p{part}' if sample else 'input', 'r') as f:
return [[int(c) for c in line.strip()] for line in f.readlines()]
def result(inp, part = 1):
res = 0;
width = len(inp[0])
height = len(inp)
lowest_h = [0 for _ in range(height)]
lowest_v = [0 for _ in range(height)]
lowest = [0 for _ in range(height)]
# get lowest in horizontal
for y, row in enumerate(inp):
for x, cell in enumerate(row):
if (x == 0 and cell < row[x+1]) \
or (x == width - 1 and cell < row[x-1]) \
or (cell < row[x-1] and cell < row[x+1]):
lowest_h[y] |= 1 << (width - x)
# get lowest in vertical
for x in range(width):
for y in range(height):
row = inp[y]
cell = row[x]
if (y == 0 and cell < inp[y+1][x]) \
or (y == height - 1 and cell < inp[y-1][x]) \
or (cell < inp[y-1][x] and cell < inp[y+1][x]):
lowest_v[y] |= 1 << (width - x)
# combine both lowests and get the overall lowests
for y in range(height):
lowest[y] = lowest_h[y] & lowest_v[y]
lowest_points = []
for y, row in enumerate(inp):
for x, cell in enumerate(row):
if lowest[y] >> (width - x) & 1 == 1:
if part == 1:
res += cell + 1
else:
lowest_points.append((x, y))
if part == 1:
return res
res = 1
verbose(lowest_points)
basins = []
for point in lowest_points:
queue = [point]
idx = 0
while idx < len(queue):
x, y = queue[idx]
for d in [(x+1, y), (x-1, y), (x, y+1), (x, y-1)]:
if d[0] >= 0 and d[0] < width and d[1] >= 0 and d[1] < height \
and d not in queue and inp[d[1]][d[0]] != 9:
queue.append(d)
idx += 1;
verbose(f"From { point = }, the region is {len(queue)}")
basins.append(len(queue))
basins.sort()
res = math.prod(basins[-3:])
return res
if __name__ == "__main__":
VERBOSE = False
print(result(get_input(), part = 2))