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path: root/3_2023.py
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import sys
import re
from collections import defaultdict

D = open(sys.argv[1]).read().strip()
lines = D.split("\n")
G = [[c for c in line] for line in lines]
R = len(G)
C = len(G[0])

p1 = 0
nums = defaultdict(list)
for r in range(len(G)):
    gears = set()  # positions of '*' characters next to the current number
    n = 0
    has_part = False
    for c in range(len(G[r]) + 1):
        if c < C and G[r][c].isdigit():
            n = n * 10 + int(G[r][c])
            for rr in [-1, 0, 1]:
                for cc in [-1, 0, 1]:
                    if 0 <= r + rr < R and 0 <= c + cc < C:
                        ch = G[r + rr][c + cc]
                        if not ch.isdigit() and ch != ".":
                            has_part = True
                        if ch == "*":
                            gears.add((r + rr, c + cc))
        elif n > 0:
            for gear in gears:
                nums[gear].append(n)
            if has_part:
                p1 += n
            n = 0
            has_part = False
            gears = set()

print(p1)
p2 = 0
for k, v in nums.items():
    if len(v) == 2:
        p2 += v[0] * v[1]
print(p2)