93 lines
2.8 KiB
Python
93 lines
2.8 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/16
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def read_file(filename: str = "input.txt") -> str:
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with open(f"{__file__.rstrip('code.py')}{filename}", "r") as f:
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return f.read().strip()
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def hex2bin(hex_str: str) -> str:
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return "".join(bin(int(h, 16))[2:].zfill(4) for h in hex_str)
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def decode_packet(packet: str) -> tuple:
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# packet header
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version = int(packet[:3], 2)
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type_id = int(packet[3: 6], 2)
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size = 6
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payload = list()
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if type_id == 4: # literal value
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for i in range(6, len(packet), 5):
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payload.append(packet[i+1: i+5])
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size += 5
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if packet[i] == "0":
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break
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payload = int("".join(payload), 2)
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else: # operator
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size += 1
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if packet[6] == "0": # length in bits of the subpacket
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sub_size = int(packet[7: 22], 2)
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size += 15 + sub_size
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data = packet[22:]
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i = 0
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while i < sub_size:
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decoded_sub = decode_packet(data[i:])
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payload.append(decoded_sub)
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i += decoded_sub[2]
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else: # packet[6] == 1, number of sub-packets
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sub_amount = int(packet[7: 18], 2)
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size += 11
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data = packet[size:]
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for i in range(sub_amount):
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decoded_sub = decode_packet(data)
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payload.append(decoded_sub)
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size += decoded_sub[2]
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data = packet[size:]
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return version, type_id, size, payload
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def sum_versions(payload: tuple) -> int:
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if payload[1] == 4:
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return payload[0]
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return payload[0] + sum(sum_versions(sub) for sub in payload[3])
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def payload_value(payload: tuple) -> int:
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# literal values
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if payload[1] == 4:
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return payload[3]
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values = [payload_value(sub) for sub in payload[3]]
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if payload[1] == 0: # sum
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return sum(values)
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elif payload[1] == 1: # product
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prod = 1
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for value in values:
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prod *= value
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return prod
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elif payload[1] == 2: # minimum
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return min(values)
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elif payload[1] == 3: # maximum
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return max(values)
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elif payload[1] == 5: # greater than
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return 1 if values[0] > values[1] else 0
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elif payload[1] == 6: # less than
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return 1 if values[0] < values[1] else 0
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else: # payload[1] == 7, equal to
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return 1 if values[0] == values[1] else 0
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def part1(hex_value: str) -> int:
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data = decode_packet(hex2bin(hex_value))
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return sum_versions(data)
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def part2(hex_value: str) -> int:
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data = decode_packet(hex2bin(hex_value))
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return payload_value(data)
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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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