71 lines
2.1 KiB
Python
71 lines
2.1 KiB
Python
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#!/usr/bin/env python3
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import copy
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import sys
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from typing import Sequence
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def part1(lines: Sequence[int], bits=12):
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gamma = 0
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epsilon = 0
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for bit in range(bits):
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mask = 1 << (bits - bit - 1)
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ones = 0
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for line in lines:
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if mask & line:
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ones += 1
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zeroes = len(lines) - ones
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if ones > zeroes:
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gamma |= mask
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else:
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epsilon |= mask
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# Fun thing - epsilon rate is just the inversion of the gamma rate.
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# However, python doesn't seem to support signed inversion so we just calculate it above. boo
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print(f"gamma: {gamma} {bin(gamma)}")
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print(f"epsilon: {epsilon} {bin(epsilon)}")
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print(f"product: {gamma * epsilon}")
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def part2(lines: Sequence[int], bits=12):
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oxygen = copy.deepcopy(lines)
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carbon = copy.deepcopy(lines)
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for bit in range(bits):
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# Find the most common bit
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if len(oxygen) > 1:
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mask = 1 << (bits - bit - 1)
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ones = 0
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for line in oxygen:
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if mask & line:
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ones += 1
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zeroes = len(oxygen) - ones
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if ones >= zeroes:
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# Filter out oxygen numbers that don't have a 1 in this position
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oxygen = [line for line in oxygen if line & mask]
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else:
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oxygen = [line for line in oxygen if not (line & mask)]
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# Now do this on the carbon array
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if len(carbon) > 1:
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ones = 0
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for line in carbon:
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if mask & line:
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ones += 1
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zeroes = len(carbon) - ones
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if ones >= zeroes:
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# Keep the *least* common
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carbon = [line for line in carbon if not (line & mask)]
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else:
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carbon = [line for line in carbon if line & mask]
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oxygen, = oxygen
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carbon, = carbon
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print(f"Oxygen: {oxygen}")
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print(f"Carbon: {carbon}")
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print(f"Product: {oxygen * carbon}")
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lines = [int(line, 2) for line in sys.stdin]
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print("Part 1")
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part1(lines)
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print("Part 2")
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part2(lines)
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