kot.pink
advent of code 2025
day 3 part 1
+29
3.py
+29
3.py
···
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import sys
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import heapq
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output_two = 0
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output_twelve = 0
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file = '3.input' if len(sys.argv) <= 1 else sys.argv[1]
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for line in open(file).readlines():
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first_seen = {} # digit to first index
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last_seen = {} # digit to last index
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for i, digit in enumerate(line.strip()):
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first_seen.setdefault(int(digit), i)
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last_seen[int(digit)] = i
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max_all = max(first_seen.keys()) # largest digit (always included)
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if last_seen[max_all] > first_seen[max_all]: # if it appears twice, just use it
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output_two += max_all * 11
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continue
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try:
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# first search right of the max digit
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max_right = max(digit for digit, i in last_seen.items() if i > first_seen[max_all])
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output_two += max_all * 10 + max_right
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except ValueError:
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# search left for max digit
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max_left = max(digit for digit, i in last_seen.items() if i < first_seen[max_all])
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output_two += max_left * 10 + max_all
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print(f'p1: {output_two}')
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print(f'p2: {output_twelve}')