63 lines
2.5 KiB
Python
63 lines
2.5 KiB
Python
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# SPDX-License-Identifier: MIT
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# Copyright (c) 2021 Akumatic
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#
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# https://adventofcode.com/2021/day/08
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def read_file(filename: str = "input.txt") -> list:
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with open(f"{__file__.rstrip('code.py')}{filename}", "r") as f:
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return [(s[0].split(), s[1].split()) for s in (line.split(" | ") for line in f.read().strip().split("\n"))]
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def remove_from_pattern(pattern: str, mask: str) -> str:
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return "".join(s for s in pattern if s not in mask)
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def find_correct_mapping(patterns: list, mask: str) -> str:
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for pattern in patterns:
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tmp = "".join(s for s in pattern if s not in mask)
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if len(tmp) == 1:
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return tmp
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def determine_mapping(patterns: list) -> dict:
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mapping = dict()
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p = [[x for x in patterns if len(x) == l] for l in range(2, 8)]
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# directly determinable
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mapping["a"] = remove_from_pattern(p[1][0], p[0][0])
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# determine g by excluding a & 4 from 9
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mapping["g"] = find_correct_mapping(p[4], p[2][0] + mapping["a"])
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# determine e by excluding a, g & 4 from 8
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mapping["e"] = remove_from_pattern(p[5][0], p[2][0] + mapping["a"] + mapping["g"])
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# determine b by excluding a, e, g & 1 from 8
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mapping["b"] = find_correct_mapping(p[4], p[0][0] + mapping["a"] + mapping["e"] + mapping["g"])
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# determine d by excluding b & 1 from 4
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mapping["d"] = remove_from_pattern(p[2][0], mapping["b"] + p[0][0])
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#determine f by excluding a, b, d & g from 5
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mapping["f"] = find_correct_mapping(p[3], mapping["a"] + mapping["b"] + mapping["d"] + mapping["g"])
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# determine c by excluding f from 1
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mapping["c"] = remove_from_pattern(p[0][0], mapping["f"])
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return mapping
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def determine_output(output: str, mapping: dict) -> int:
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digits = {"abcefg" : 0, "cf": 1, "acdeg": 2, "acdfg": 3, "bcdf": 4, "abdfg": 5,
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"abdefg": 6, "acf": 7, "abcdefg": 8, "abcdfg": 9}
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tmp = [mapping[x] for x in output]
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tmp.sort()
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return digits["".join(tmp)]
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def part1(vals: list) -> int:
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count = 0
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for val in vals:
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count += sum(1 for x in val[1] if len(x) in [2, 3, 4, 7])
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return count
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def part2(vals: list) -> int:
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result = 0
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for val in vals:
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mapping = determine_mapping(val[0])
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decode_mapping = {mapping[key]: key for key in mapping}
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tmp = [determine_output(x, decode_mapping) for x in val[1]]
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result += 1000 * tmp[0] + 100 * tmp[1] + 10 * tmp[2] + tmp[3]
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return result
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if __name__ == "__main__":
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vals = read_file()
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print(f"Part 1: {part1(vals)}")
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print(f"Part 2: {part2(vals)}")
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