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| 1 | +use common::sfy::Sfy; |
| 2 | +use regex::Regex; |
| 3 | + |
| 4 | +pub fn run(input: &[u8]) { |
| 5 | + println!("pro-tip: compile with --release!"); |
| 6 | + let part1 = solve_part1(input).sfy(); |
| 7 | + println!("part 1: {}", part1); |
| 8 | + assert_eq!(part1, "bkgcdefiholnpmja"); |
| 9 | + |
| 10 | + let part2 = solve_part2(input, 1000000000).sfy(); |
| 11 | + println!("part 2: {}", part2); |
| 12 | + assert_eq!(part2, "knmdfoijcbpghlea"); |
| 13 | +} |
| 14 | + |
| 15 | +fn solve_part1(input: &[u8]) -> Vec<u8> { |
| 16 | + let a = "abcdefghijklmnop"; |
| 17 | + return transform(input.sfy(), a.as_bytes()); |
| 18 | +} |
| 19 | + |
| 20 | +fn solve_part2(input: &[u8], iter: usize) -> Vec<u8> { |
| 21 | + let a = "abcdefghijklmnop".as_bytes(); |
| 22 | + |
| 23 | + // measure cycle |
| 24 | + let mut b: Vec<u8> = a.to_vec(); |
| 25 | + let mut cycle = 0; |
| 26 | + loop { |
| 27 | + b = transform(input.sfy(), &b); |
| 28 | + cycle += 1; |
| 29 | + if a.to_vec() == b { |
| 30 | + break; |
| 31 | + } |
| 32 | + } |
| 33 | + println!("cycle length: {}", cycle); |
| 34 | + |
| 35 | + // perform iter modulo cycle transformations |
| 36 | + let mut b = a.to_vec(); |
| 37 | + for _ in 0..(iter % cycle) { |
| 38 | + b = transform(input.sfy(), &b); |
| 39 | + } |
| 40 | + return b; |
| 41 | +} |
| 42 | + |
| 43 | +fn transform(moves: String, state: &[u8]) -> Vec<u8> { |
| 44 | + let L = state.len(); |
| 45 | + let mut r = Vec::new(); |
| 46 | + for i in 0..L { |
| 47 | + r.push(state[i]); |
| 48 | + } |
| 49 | + |
| 50 | + let re_s = Regex::new(r"s([0-9]+)").unwrap(); |
| 51 | + let re_x = Regex::new(r"x([0-9]+)/([0-9]+)").unwrap(); |
| 52 | + let re_p = Regex::new(r"p([a-z]+)/([a-z]+)").unwrap(); |
| 53 | + |
| 54 | + for m in moves.split(",") { |
| 55 | + let cap = re_s.captures(m); |
| 56 | + if cap.is_some() { |
| 57 | + let spin: usize = cap.unwrap().get(1).unwrap().as_str().parse().unwrap(); |
| 58 | + let t = r.clone(); |
| 59 | + for i in 0..state.len() { |
| 60 | + r[(i + spin) % L] = t[i]; |
| 61 | + } |
| 62 | + continue; |
| 63 | + } |
| 64 | + let cap = re_x.captures(m); |
| 65 | + if cap.is_some() { |
| 66 | + let cap = cap.unwrap(); |
| 67 | + let a: usize = cap.get(1).unwrap().as_str().parse().unwrap(); |
| 68 | + let b: usize = cap.get(2).unwrap().as_str().parse().unwrap(); |
| 69 | + let t = r[a]; |
| 70 | + r[a] = r[b]; |
| 71 | + r[b] = t; |
| 72 | + continue; |
| 73 | + } |
| 74 | + let cap = re_p.captures(m); |
| 75 | + if cap.is_some() { |
| 76 | + let cap = cap.unwrap(); |
| 77 | + let pa: &str = cap.get(1).unwrap().as_str(); |
| 78 | + let pb: &str = cap.get(2).unwrap().as_str(); |
| 79 | + let a = r.iter().position(|&c| c == pa.as_bytes()[0]).unwrap(); |
| 80 | + let b = r.iter().position(|&c| c == pb.as_bytes()[0]).unwrap(); |
| 81 | + |
| 82 | + let t = r[a]; |
| 83 | + r[a] = r[b]; |
| 84 | + r[b] = t; |
| 85 | + continue; |
| 86 | + } |
| 87 | + panic!("invalid input: {}", m); |
| 88 | + } |
| 89 | + |
| 90 | + return r; |
| 91 | +} |
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