Add input files day 18

By brute force and lots of it

2021/inputs/19.txt

@@ -0,0 +1,921 @@
+--- scanner 0 ---
+-377,550,716
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+
+--- scanner 1 ---
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+
+--- scanner 2 ---
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+
+--- scanner 3 ---
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+702,620,743
+
+--- scanner 4 ---
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+
+--- scanner 5 ---
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+
+--- scanner 6 ---
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+
+--- scanner 7 ---
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+
+--- scanner 8 ---
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+
+--- scanner 9 ---
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+
+--- scanner 10 ---
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+
+--- scanner 11 ---
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+
+--- scanner 12 ---
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+
+--- scanner 13 ---
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+
+--- scanner 14 ---
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+
+--- scanner 15 ---
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+
+--- scanner 16 ---
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+
+--- scanner 17 ---
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+
+--- scanner 18 ---
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+
+--- scanner 19 ---
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+
+--- scanner 20 ---
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+
+--- scanner 21 ---
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+
+--- scanner 22 ---
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+
+--- scanner 23 ---
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+
+--- scanner 24 ---
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+
+--- scanner 25 ---
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+
+--- scanner 26 ---
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+
+--- scanner 27 ---
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+
+--- scanner 28 ---
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+
+--- scanner 29 ---
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+
+--- scanner 30 ---
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+
+--- scanner 31 ---
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+
+--- scanner 32 ---
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+-813,-584,814

2021/src/common.rs

@@ -82,8 +82,9 @@ pub fn ordered<O: PartialOrd>(a: O, b: O) -> (O, O) {
     }
 }
 
-pub fn read_input<P, O>(input: &mut dyn Read, parser: P) -> O
+pub fn read_input<I, P, O>(mut input: I, parser: P) -> O
 where
+    I: Read,
     P: for<'a> FnOnce(&'a [u8]) -> IResult<&'a [u8], O>,
 {
     let mut buffer = Vec::new();

2021/src/day19.rs

@@ -1,9 +1,290 @@
+use std::collections::HashSet;
 use std::io::Read;
+use std::ops::Add;
+use std::ops::Sub;
 
-pub fn part1(_input: &mut dyn Read) -> String {
-    todo!()
+use nom::bytes::complete::tag;
+use nom::character::complete::newline;
+use nom::combinator::map;
+use nom::multi::many1;
+use nom::multi::separated_list1;
+use nom::sequence::delimited;
+use nom::sequence::preceded;
+use nom::sequence::terminated;
+use nom::sequence::tuple;
+use nom::IResult;
+
+use crate::common::read_input;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Default)]
+struct Point3(pub [i32; 3]);
+
+impl Point3 {
+    pub fn manhattan(&self) -> i32 {
+        self.0.into_iter().map(i32::abs).sum()
+    }
 }
 
-pub fn part2(_input: &mut dyn Read) -> String {
-    todo!()
+impl Sub for Point3 {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Point3([
+            self.0[0] - rhs.0[0],
+            self.0[1] - rhs.0[1],
+            self.0[2] - rhs.0[2],
+        ])
+    }
+}
+
+impl Add for Point3 {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Point3([
+            self.0[0] + rhs.0[0],
+            self.0[1] + rhs.0[1],
+            self.0[2] + rhs.0[2],
+        ])
+    }
+}
+
+struct Rotations<'a> {
+    points: &'a [Point3],
+    axes: [usize; 3],
+    rotation_index: usize,
+}
+
+impl<'a> Rotations<'a> {
+    const ROTATIONS: [[i32; 3]; 8] = [
+        [1, 1, 1],
+        [1, 1, -1],
+        [1, -1, 1],
+        [1, -1, -1],
+        [-1, 1, 1],
+        [-1, 1, -1],
+        [-1, -1, 1],
+        [-1, -1, -1],
+    ];
+
+    pub fn new(points: &'a [Point3]) -> Self {
+        Self {
+            points,
+            axes: [0, 1, 2],
+            rotation_index: 0,
+        }
+    }
+}
+
+impl Iterator for Rotations<'_> {
+    type Item = Vec<Point3>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.rotation_index >= Self::ROTATIONS.len() {
+            if !next_permutation(&mut self.axes) {
+                return None;
+            }
+
+            self.rotation_index = 0;
+        }
+
+        let axes = &self.axes;
+        let rot = &Self::ROTATIONS[self.rotation_index];
+
+        let result = self
+            .points
+            .iter()
+            .map(|Point3(coords)| {
+                Point3([
+                    coords[axes[0]] * rot[0],
+                    coords[axes[1]] * rot[1],
+                    coords[axes[2]] * rot[2],
+                ])
+            })
+            .collect();
+
+        self.rotation_index += 1;
+
+        Some(result)
+    }
+}
+
+fn parse_point(input: &[u8]) -> IResult<&[u8], Point3> {
+    use nom::character::complete::char;
+    use nom::character::complete::i32;
+
+    map(
+        tuple((i32, preceded(char(','), i32), preceded(char(','), i32))),
+        |(x, y, z)| Point3([x, y, z]),
+    )(input)
+}
+
+fn parse_input(input: &[u8]) -> IResult<&[u8], Vec<Vec<Point3>>> {
+    use nom::character::complete::i32;
+    let parse_header = delimited(tag("--- scanner "), i32, tag(" ---\n"));
+
+    let parse_scanner = preceded(parse_header, many1(terminated(parse_point, newline)));
+    separated_list1(newline, parse_scanner)(input)
+}
+
+fn try_overlap(
+    correct: &[(Point3, HashSet<Point3>)],
+    candidate: &[Point3],
+) -> Option<(Point3, Vec<Point3>)> {
+    let mut relative = HashSet::new();
+    for rot in Rotations::new(candidate) {
+        for &start in &rot {
+            relative.clear();
+
+            relative.extend(rot.iter().map(|&other| other - start));
+
+            if let Some((base, _)) = correct.iter().find(|(_, correct_relative)| {
+                correct_relative.intersection(&relative).count() >= 12
+            }) {
+                // Found a solution, build the correct output
+                let translated = relative.drain().map(|point| point + *base).collect();
+
+                return Some((start - *base, translated));
+            }
+        }
+    }
+
+    None
+}
+
+fn parts_common(input: &mut dyn Read) -> (HashSet<Point3>, Vec<Point3>) {
+    let mut scanners = read_input(input, parse_input);
+
+    let mut points: HashSet<_> = scanners[0].iter().copied().collect();
+
+    let mut todo = vec![std::mem::take(&mut scanners[0])];
+    let mut scanners_found = vec![Point3::default()];
+
+    while let Some(matched) = todo.pop() {
+        if scanners.iter().all(Vec::is_empty) {
+            break;
+        }
+
+        let relative: Vec<(Point3, HashSet<Point3>)> = matched
+            .iter()
+            .map(|&base| (base, matched.iter().map(|&other| (other - base)).collect()))
+            .collect();
+
+        for candidate in &mut scanners {
+            if candidate.is_empty() {
+                continue;
+            }
+
+            if let Some((scanner, result)) = try_overlap(&relative, candidate) {
+                scanners_found.push(scanner);
+                points.extend(result.iter().copied());
+                todo.push(result);
+                candidate.clear();
+            }
+        }
+    }
+
+    (points, scanners_found)
+}
+
+pub fn part1(input: &mut dyn Read) -> String {
+    let (points, _) = parts_common(input);
+    points.len().to_string()
+}
+
+pub fn part2(input: &mut dyn Read) -> String {
+    let (_, scanners) = parts_common(input);
+
+    scanners
+        .iter()
+        .flat_map(|&first| {
+            scanners
+                .iter()
+                .map(move |&second| (first - second).manhattan())
+        })
+        .max()
+        .unwrap()
+        .to_string()
+}
+
+pub fn next_permutation<T: Ord>(list: &mut [T]) -> bool {
+    // Based on: https://en.cppreference.com/w/cpp/algorithm/next_permutation
+    if list.len() <= 1 {
+        return false;
+    }
+
+    if let Some((i, val1)) = list
+        .windows(2)
+        .enumerate()
+        .rev()
+        .find_map(|(i, window)| (window[0] < window[1]).then(|| (i, &window[0])))
+    {
+        let it2 = list
+            .iter()
+            .enumerate()
+            .skip(i + 1)
+            .rev()
+            .find_map(|(idx, val2)| (val1 < val2).then(|| idx))
+            .expect("Unreachable, ascending pair exists");
+
+        list.swap(i, it2);
+        list[(i + 1)..].reverse();
+        true
+    } else {
+        list.reverse();
+        false
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::test_implementation;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/19.txt");
+
+    #[test]
+    fn test_next_permutation() {
+        let mut list = [1, 2, 3];
+
+        assert!(next_permutation(&mut list));
+        assert_eq!(list, [1, 3, 2]);
+
+        assert!(next_permutation(&mut list));
+        assert_eq!(list, [2, 1, 3]);
+
+        assert!(next_permutation(&mut list));
+        assert_eq!(list, [2, 3, 1]);
+
+        assert!(next_permutation(&mut list));
+        assert_eq!(list, [3, 1, 2]);
+
+        assert!(next_permutation(&mut list));
+        assert_eq!(list, [3, 2, 1]);
+
+        // Note the negation!
+        assert!(!next_permutation(&mut list));
+        assert_eq!(list, [1, 2, 3]);
+
+        // 24 is a bit too much to write out, but we can check the number
+        let mut list2 = [1, 2, 3, 4];
+        for _ in 1..24 {
+            assert!(next_permutation(&mut list2));
+        }
+
+        // Should be back to the start
+        assert!(!next_permutation(&mut list2));
+        assert_eq!(list2, [1, 2, 3, 4]);
+    }
+
+    #[test]
+    fn sample_part1() {
+        test_implementation(part1, SAMPLE, 79);
+    }
+
+    #[test]
+    fn sample_part2() {
+        test_implementation(part2, SAMPLE, 3621);
+    }
 }

2021/src/samples/19.txt

@@ -0,0 +1,136 @@
+--- scanner 0 ---
+404,-588,-901
+528,-643,409
+-838,591,734
+390,-675,-793
+-537,-823,-458
+-485,-357,347
+-345,-311,381
+-661,-816,-575
+-876,649,763
+-618,-824,-621
+553,345,-567
+474,580,667
+-447,-329,318
+-584,868,-557
+544,-627,-890
+564,392,-477
+455,729,728
+-892,524,684
+-689,845,-530
+423,-701,434
+7,-33,-71
+630,319,-379
+443,580,662
+-789,900,-551
+459,-707,401
+
+--- scanner 1 ---
+686,422,578
+605,423,415
+515,917,-361
+-336,658,858
+95,138,22
+-476,619,847
+-340,-569,-846
+567,-361,727
+-460,603,-452
+669,-402,600
+729,430,532
+-500,-761,534
+-322,571,750
+-466,-666,-811
+-429,-592,574
+-355,545,-477
+703,-491,-529
+-328,-685,520
+413,935,-424
+-391,539,-444
+586,-435,557
+-364,-763,-893
+807,-499,-711
+755,-354,-619
+553,889,-390
+
+--- scanner 2 ---
+649,640,665
+682,-795,504
+-784,533,-524
+-644,584,-595
+-588,-843,648
+-30,6,44
+-674,560,763
+500,723,-460
+609,671,-379
+-555,-800,653
+-675,-892,-343
+697,-426,-610
+578,704,681
+493,664,-388
+-671,-858,530
+-667,343,800
+571,-461,-707
+-138,-166,112
+-889,563,-600
+646,-828,498
+640,759,510
+-630,509,768
+-681,-892,-333
+673,-379,-804
+-742,-814,-386
+577,-820,562
+
+--- scanner 3 ---
+-589,542,597
+605,-692,669
+-500,565,-823
+-660,373,557
+-458,-679,-417
+-488,449,543
+-626,468,-788
+338,-750,-386
+528,-832,-391
+562,-778,733
+-938,-730,414
+543,643,-506
+-524,371,-870
+407,773,750
+-104,29,83
+378,-903,-323
+-778,-728,485
+426,699,580
+-438,-605,-362
+-469,-447,-387
+509,732,623
+647,635,-688
+-868,-804,481
+614,-800,639
+595,780,-596
+
+--- scanner 4 ---
+727,592,562
+-293,-554,779
+441,611,-461
+-714,465,-776
+-743,427,-804
+-660,-479,-426
+832,-632,460
+927,-485,-438
+408,393,-506
+466,436,-512
+110,16,151
+-258,-428,682
+-393,719,612
+-211,-452,876
+808,-476,-593
+-575,615,604
+-485,667,467
+-680,325,-822
+-627,-443,-432
+872,-547,-609
+833,512,582
+807,604,487
+839,-516,451
+891,-625,532
+-652,-548,-490
+30,-46,-14