josh
d6bd55ad1b
Reviewed-on: #1 Co-authored-by: josh <josh@joshuaschuett.com> Co-committed-by: josh <josh@joshuaschuett.com>
96 lines
2.3 KiB
Python
96 lines
2.3 KiB
Python
#!/usr/bin/env python3
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"""
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Counts how many reports are "safe".
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A report (one line of space-separated integers) is safe if:
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1) Levels are strictly monotonic (all increasing OR all decreasing).
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2) Adjacent levels differ by at least 1 and at most 3 (inclusive).
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Usage:
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python day2/aoc_2024_day2.py input.txt
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"""
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import argparse
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class Report:
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def __init__(self, levels):
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self.levels = levels
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@classmethod
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def from_line(cls, line):
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parts = line.split()
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levels = []
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for part in parts:
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levels.append(int(part))
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return cls(levels=levels)
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def is_safe(self):
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if len(self.levels) < 2:
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return True
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# Determine direction (increasing/decreasing) from the first valid step.
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# 0 => not decided yet
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# +1 => increasing
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# -1 => decreasing
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direction = 0
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for i in range(1, len(self.levels)):
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previous_level = self.levels[i - 1]
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current_level = self.levels[i]
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delta = current_level - previous_level
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# Adjacent levels must change (no equals).
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if delta == 0:
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return False
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# Differ by at least one and at most three.
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if abs(delta) > 3:
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return False
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step_direction = 1 if delta > 0 else -1
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if direction == 0:
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direction = step_direction
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# The levels are either all increasing or all decreasing.
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elif step_direction != direction:
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return False
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return True
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def parse_reports(path):
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reports = []
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with open(path, "r", encoding="utf-8") as f:
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for raw in f:
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line = raw.strip()
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if not line:
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continue
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reports.append(Report.from_line(line))
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return reports
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def count_safe(reports):
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safe_count = 0
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for report in reports:
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if report.is_safe():
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safe_count += 1
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return safe_count
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def count_safe_in_file(path):
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return count_safe(parse_reports(path))
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def main(argv=None):
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parser = argparse.ArgumentParser("CLI to read sample files.")
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parser.add_argument(
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"input",
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help="Input file path.",
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)
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args = parser.parse_args(argv)
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return count_safe_in_file(args.input)
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if __name__ == "__main__":
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print(main()) |