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| 1 | +advent_of_code::solution!(24); |
| 2 | + |
| 3 | +use advent_of_code::maneatingape::hash::*; |
| 4 | +use advent_of_code::maneatingape::parse::*; |
| 5 | + |
| 6 | +#[derive(Hash, Eq, PartialEq, Clone, Copy)] |
| 7 | +enum Operator { |
| 8 | + And, |
| 9 | + Or, |
| 10 | + Xor, |
| 11 | +} |
| 12 | + |
| 13 | +type Gate<'a> = (&'a str, Operator, &'a str, &'a str); |
| 14 | + |
| 15 | +fn parse_data(input: &str) -> (Vec<bool>, Vec<Gate>) { |
| 16 | + let (left, right) = input.split_once("\n\n").unwrap(); |
| 17 | + |
| 18 | + let inputs = left.lines().map(|line| &line[5..] == "1").collect(); |
| 19 | + |
| 20 | + let gates = right |
| 21 | + .lines() |
| 22 | + .map(|line| { |
| 23 | + let mut iter = line.split_ascii_whitespace(); |
| 24 | + let l = iter.next().unwrap(); |
| 25 | + let op = iter.next().unwrap(); |
| 26 | + let r = iter.next().unwrap(); |
| 27 | + let res = iter.last().unwrap(); |
| 28 | + |
| 29 | + let operator = match op { |
| 30 | + "AND" => Operator::And, |
| 31 | + "OR" => Operator::Or, |
| 32 | + "XOR" => Operator::Xor, |
| 33 | + _ => unreachable!(), |
| 34 | + }; |
| 35 | + |
| 36 | + (l, operator, r, res) |
| 37 | + }) |
| 38 | + .collect(); |
| 39 | + |
| 40 | + (inputs, gates) |
| 41 | +} |
| 42 | + |
| 43 | +fn find_max_z_number(gates: &[Gate]) -> usize { |
| 44 | + let z_count = gates |
| 45 | + .iter() |
| 46 | + .filter(|(_, _, _, res)| res.starts_with("z")) |
| 47 | + .count(); |
| 48 | + |
| 49 | + z_count - 1 |
| 50 | +} |
| 51 | + |
| 52 | +fn solve( |
| 53 | + input_x: &[bool], |
| 54 | + input_y: &[bool], |
| 55 | + gates_rev: &FastMap<&str, (&str, Operator, &str)>, |
| 56 | + name: &str, |
| 57 | +) -> bool { |
| 58 | + if name.starts_with("x") { |
| 59 | + return input_x[name.unsigned::<usize>()]; |
| 60 | + } |
| 61 | + |
| 62 | + if name.starts_with("y") { |
| 63 | + return input_y[name.unsigned::<usize>()]; |
| 64 | + } |
| 65 | + |
| 66 | + let (left_name, operator, right_name) = &gates_rev[name]; |
| 67 | + let left = solve(input_x, input_y, gates_rev, left_name); |
| 68 | + let right = solve(input_x, input_y, gates_rev, right_name); |
| 69 | + |
| 70 | + match operator { |
| 71 | + Operator::And => left & right, |
| 72 | + Operator::Or => left | right, |
| 73 | + Operator::Xor => left ^ right, |
| 74 | + } |
| 75 | +} |
| 76 | + |
| 77 | +pub fn part_one(input: &str) -> Option<u64> { |
| 78 | + let (inputs, gates) = parse_data(input); |
| 79 | + |
| 80 | + let max_z_number = find_max_z_number(&gates); |
| 81 | + |
| 82 | + let gates_rev = gates |
| 83 | + .into_iter() |
| 84 | + .map(|(l, o, r, res)| (res, (l, o, r))) |
| 85 | + .collect::<FastMap<_, _>>(); |
| 86 | + |
| 87 | + let mut result = 0; |
| 88 | + |
| 89 | + let x = &inputs[..inputs.len() / 2]; |
| 90 | + let y = &inputs[inputs.len() / 2..]; |
| 91 | + for i in 0..=max_z_number { |
| 92 | + let z = solve(x, y, &gates_rev, &format!("z{:02}", i)); |
| 93 | + result |= (z as u64) << i; |
| 94 | + } |
| 95 | + |
| 96 | + Some(result) |
| 97 | +} |
| 98 | + |
| 99 | +/* |
| 100 | + x_0 XOR y_0 = z_0 |
| 101 | + x_0 AND y_0 = c_0 |
| 102 | + for i in 1..z_max { |
| 103 | + x_i XOR y_i = s_i_0 |
| 104 | + x_i AND y_i = c_i_0 |
| 105 | + c_{i-1} XOR s_i_0 = z_i |
| 106 | + c_{i-1} AND s_i_0 = c_i_1 |
| 107 | + c_i_0 OR c_i_1 = c_i |
| 108 | + } |
| 109 | +*/ |
| 110 | +pub fn part_two(input: &str) -> Option<String> { |
| 111 | + let (_, gates) = parse_data(input); |
| 112 | + |
| 113 | + let input_with_operator = gates |
| 114 | + .iter() |
| 115 | + .flat_map(|(l, o, r, _)| [(*l, *o), (*r, *o)]) |
| 116 | + .collect::<FastSet<_>>(); |
| 117 | + |
| 118 | + let max_z_name = format!("z{:02}", find_max_z_number(&gates)); |
| 119 | + |
| 120 | + let mut result = gates |
| 121 | + .into_iter() |
| 122 | + .filter(|&(input, operator, _, res)| { |
| 123 | + if input == "x00" || input == "y00" { |
| 124 | + if operator == Operator::Xor && res != "z00" { |
| 125 | + return true; |
| 126 | + } |
| 127 | + |
| 128 | + if operator == Operator::And && res.starts_with("z") { |
| 129 | + return true; |
| 130 | + } |
| 131 | + |
| 132 | + return false; |
| 133 | + } |
| 134 | + |
| 135 | + if operator == Operator::Xor { |
| 136 | + if input.starts_with("x") || input.starts_with("y") { |
| 137 | + if !input_with_operator.contains(&(res, Operator::Xor)) { |
| 138 | + return true; |
| 139 | + } |
| 140 | + |
| 141 | + if !input_with_operator.contains(&(res, Operator::And)) { |
| 142 | + return true; |
| 143 | + } |
| 144 | + |
| 145 | + if res.starts_with("z") { |
| 146 | + return true; |
| 147 | + } |
| 148 | + } else if !res.starts_with("z") { |
| 149 | + return true; |
| 150 | + } |
| 151 | + } |
| 152 | + |
| 153 | + if operator == Operator::And { |
| 154 | + if res.starts_with("z") { |
| 155 | + return true; |
| 156 | + } |
| 157 | + |
| 158 | + if (input.starts_with("x") || input.starts_with("y")) |
| 159 | + && !input_with_operator.contains(&(res, Operator::Or)) |
| 160 | + { |
| 161 | + return true; |
| 162 | + } |
| 163 | + } |
| 164 | + |
| 165 | + if operator == Operator::Or && res.starts_with("z") && res != max_z_name { |
| 166 | + return true; |
| 167 | + } |
| 168 | + |
| 169 | + false |
| 170 | + }) |
| 171 | + .map(|(_, _, _, res)| res) |
| 172 | + .collect::<Vec<_>>(); |
| 173 | + |
| 174 | + result.sort_unstable(); |
| 175 | + let result = result.join(","); |
| 176 | + |
| 177 | + Some(result) |
| 178 | +} |
| 179 | + |
| 180 | +#[cfg(test)] |
| 181 | +mod tests { |
| 182 | + use super::*; |
| 183 | + |
| 184 | + #[test] |
| 185 | + fn test_part_one() { |
| 186 | + let input = advent_of_code::template::read_file_part("examples", DAY, 1); |
| 187 | + let result = part_one(&input); |
| 188 | + assert_eq!(result, Some(2024)); |
| 189 | + } |
| 190 | + |
| 191 | + #[test] |
| 192 | + fn test_part_two() { |
| 193 | + let input = advent_of_code::template::read_file_part("examples", DAY, 2); |
| 194 | + let result = part_two(&input); |
| 195 | + assert_eq!( |
| 196 | + result, |
| 197 | + Some(String::from("e01,e04,q01,q03,w01,z00,z03,z04")) |
| 198 | + ); |
| 199 | + } |
| 200 | +} |
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