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