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| 1 | +//! [Day 10: Factory](https://adventofcode.com/2025/day/10) |
| 2 | +
|
| 3 | +use z3::ast::Int; |
| 4 | + |
| 5 | +struct Machine { |
| 6 | + lights: u32, |
| 7 | + wirings: Vec<u32>, |
| 8 | + joltages: Vec<u32>, |
| 9 | +} |
| 10 | + |
| 11 | +impl Machine { |
| 12 | + /// Returns fewest required presses to correctly configure the indicator lights of the machine. |
| 13 | + fn score(&self) -> Option<usize> { |
| 14 | + (0..(1u32 << self.wirings.len())) |
| 15 | + .filter_map(|k| { |
| 16 | + let mut result = 0; |
| 17 | + let mut k_score = 0; |
| 18 | + |
| 19 | + for (i, wiring) in self.wirings.iter().enumerate() { |
| 20 | + if k & (1 << i) != 0 { |
| 21 | + // press button, xor toggles the lights |
| 22 | + result ^= wiring; |
| 23 | + k_score += 1; |
| 24 | + } |
| 25 | + } |
| 26 | + |
| 27 | + if result == self.lights { |
| 28 | + Some(k_score) |
| 29 | + } else { |
| 30 | + None |
| 31 | + } |
| 32 | + }) |
| 33 | + .min() |
| 34 | + } |
| 35 | + |
| 36 | + /// Return the fewest button presses required to correctly configure the joltage level counters . |
| 37 | + fn optimize(&self) -> u64 { |
| 38 | + let solver = z3::Optimize::new(); |
| 39 | + |
| 40 | + let vars: Vec<_> = (0..self.wirings.len()) |
| 41 | + .map(|i| Int::new_const(format!("w{i}"))) |
| 42 | + .collect(); |
| 43 | + |
| 44 | + for v in &vars { |
| 45 | + solver.assert(&v.ge(Int::from_u64(0))); |
| 46 | + } |
| 47 | + |
| 48 | + for (i, &target) in self.joltages.iter().enumerate() { |
| 49 | + let mut terms = Vec::new(); |
| 50 | + for (j, w) in self.wirings.iter().enumerate() { |
| 51 | + if w & (1 << i) != 0 { |
| 52 | + terms.push(vars[j].clone()); |
| 53 | + } |
| 54 | + } |
| 55 | + |
| 56 | + let sum = if terms.is_empty() { |
| 57 | + Int::from_u64(0) |
| 58 | + } else { |
| 59 | + Int::add(&terms.iter().collect::<Vec<_>>()) |
| 60 | + }; |
| 61 | + solver.assert(&sum.eq(Int::from_u64(target.into()))); |
| 62 | + } |
| 63 | + |
| 64 | + let sum_vars = z3::ast::Int::add(&vars.iter().collect::<Vec<_>>()); |
| 65 | + solver.minimize(&sum_vars); |
| 66 | + |
| 67 | + match solver.check(&[]) { |
| 68 | + z3::SatResult::Sat => { |
| 69 | + let model = solver.get_model().unwrap(); |
| 70 | + vars.iter() |
| 71 | + .filter_map(|v| { |
| 72 | + let val = model.get_const_interp(v).unwrap(); |
| 73 | + val.as_u64() |
| 74 | + }) |
| 75 | + .sum() |
| 76 | + } |
| 77 | + _ => 0, |
| 78 | + } |
| 79 | + } |
| 80 | +} |
| 81 | + |
| 82 | +struct Puzzle { |
| 83 | + machines: Vec<Machine>, |
| 84 | +} |
| 85 | + |
| 86 | +impl Puzzle { |
| 87 | + /// Initialize from the puzzle input. |
| 88 | + fn new(data: &str) -> Self { |
| 89 | + let mut machines = vec![]; |
| 90 | + for line in data.lines() { |
| 91 | + let p: Vec<_> = line.split_ascii_whitespace().collect(); |
| 92 | + |
| 93 | + // parse the indicator lights |
| 94 | + let mut lights = 0; |
| 95 | + for (k, light) in p[0] |
| 96 | + .strip_prefix('[') |
| 97 | + .unwrap() |
| 98 | + .strip_suffix(']') |
| 99 | + .unwrap() |
| 100 | + .chars() |
| 101 | + .enumerate() |
| 102 | + { |
| 103 | + if light == '#' { |
| 104 | + lights += 1 << k; |
| 105 | + } |
| 106 | + } |
| 107 | + |
| 108 | + // parse the button wiring schematics |
| 109 | + let mut wirings = vec![]; |
| 110 | + for w in &p[1..p.len() - 1] { |
| 111 | + wirings.push( |
| 112 | + w.strip_prefix('(') |
| 113 | + .unwrap() |
| 114 | + .strip_suffix(')') |
| 115 | + .unwrap() |
| 116 | + .split(',') |
| 117 | + .map(|s: &str| 1u32 << s.parse::<u32>().unwrap()) |
| 118 | + .sum(), |
| 119 | + ); |
| 120 | + } |
| 121 | + |
| 122 | + // parse the joltage requirements |
| 123 | + let joltages = p |
| 124 | + .last() |
| 125 | + .unwrap() |
| 126 | + .strip_prefix('{') |
| 127 | + .unwrap() |
| 128 | + .strip_suffix('}') |
| 129 | + .unwrap() |
| 130 | + .split(',') |
| 131 | + .map(|s: &str| s.parse::<u32>().unwrap()) |
| 132 | + .collect(); |
| 133 | + |
| 134 | + machines.push(Machine { |
| 135 | + lights, |
| 136 | + wirings, |
| 137 | + joltages, |
| 138 | + }); |
| 139 | + } |
| 140 | + Self { machines } |
| 141 | + } |
| 142 | + |
| 143 | + /// Solve part one. |
| 144 | + fn part1(&self) -> usize { |
| 145 | + self.machines.iter().filter_map(Machine::score).sum() |
| 146 | + } |
| 147 | + |
| 148 | + /// Solve part two. |
| 149 | + fn part2(&self) -> u64 { |
| 150 | + self.machines.iter().map(Machine::optimize).sum() |
| 151 | + } |
| 152 | +} |
| 153 | + |
| 154 | +/// # Panics |
| 155 | +#[must_use] |
| 156 | +pub fn solve(data: &str) -> (usize, u64) { |
| 157 | + let puzzle = Puzzle::new(data); |
| 158 | + (puzzle.part1(), puzzle.part2()) |
| 159 | +} |
| 160 | + |
| 161 | +pub fn main() { |
| 162 | + let args = aoc::parse_args(); |
| 163 | + args.run(solve); |
| 164 | +} |
| 165 | + |
| 166 | +#[cfg(test)] |
| 167 | +mod test { |
| 168 | + use super::*; |
| 169 | + |
| 170 | + const TEST_INPUT: &str = include_str!("test.txt"); |
| 171 | + |
| 172 | + #[test] |
| 173 | + fn part1() { |
| 174 | + let puzzle = Puzzle::new(TEST_INPUT); |
| 175 | + assert_eq!(puzzle.part1(), 7); |
| 176 | + } |
| 177 | + |
| 178 | + #[test] |
| 179 | + fn part2() { |
| 180 | + let puzzle = Puzzle::new(TEST_INPUT); |
| 181 | + assert_eq!(puzzle.part2(), 33); |
| 182 | + } |
| 183 | +} |
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