Day 10 - Part 1

Signed-off-by: Anthony Oteri <anthony.oteri@gmail.com>
2026-06-06 00:46:53 -04:00 · 2023-12-11 12:18:51 -05:00
parent 114073c205
commit 2a950bdcb4
11 changed files with 448 additions and 0 deletions
@@ -0,0 +1,181 @@
+use crate::error::AocError;
+use std::collections::BTreeMap;
+
+#[derive(Debug, Clone, Eq, PartialEq, Default, Ord, PartialOrd)]
+struct Point {
+    row: i32,
+    col: i32,
+}
+
+#[derive(Debug, Clone, Eq, PartialEq, Default)]
+struct Pipe {
+    input: Point,
+    output: Point,
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+enum Tile {
+    Vertical(Pipe),
+    Horizontal(Pipe),
+    NorthEast(Pipe),
+    NorthWest(Pipe),
+    SouthWest(Pipe),
+    SouteEast(Pipe),
+    Ground,
+    Start,
+}
+
+fn parse(input: &str) -> BTreeMap<Point, Tile> {
+    let grid = input
+        .lines()
+        .enumerate()
+        .flat_map(|(row, line)| {
+            line.chars().enumerate().map(move |(col, c)| {
+                let pos = Point {
+                    row: row as i32,
+                    col: col as i32,
+                };
+
+                let tile = match c {
+                    '|' => Tile::Vertical(Pipe {
+                        input: Point {
+                            row: pos.row - 1,
+                            col: pos.col,
+                        },
+                        output: Point {
+                            row: pos.row + 1,
+                            col: pos.col,
+                        },
+                    }),
+                    '-' => Tile::Horizontal(Pipe {
+                        input: Point {
+                            row: pos.row,
+                            col: pos.col - 1,
+                        },
+                        output: Point {
+                            row: pos.row,
+                            col: pos.col + 1,
+                        },
+                    }),
+                    'L' => Tile::NorthEast(Pipe {
+                        input: Point {
+                            row: pos.row - 1,
+                            col: pos.col,
+                        },
+                        output: Point {
+                            row: pos.row,
+                            col: pos.col + 1,
+                        },
+                    }),
+                    'J' => Tile::NorthWest(Pipe {
+                        input: Point {
+                            row: pos.row - 1,
+                            col: pos.col,
+                        },
+                        output: Point {
+                            row: pos.row,
+                            col: pos.col - 1,
+                        },
+                    }),
+                    '7' => Tile::SouthWest(Pipe {
+                        input: Point {
+                            row: pos.row + 1,
+                            col: pos.col,
+                        },
+                        output: Point {
+                            row: pos.row,
+                            col: pos.col - 1,
+                        },
+                    }),
+                    'F' => Tile::SouteEast(Pipe {
+                        input: Point {
+                            row: pos.row + 1,
+                            col: pos.col,
+                        },
+                        output: Point {
+                            row: pos.row,
+                            col: pos.col + 1,
+                        },
+                    }),
+                    '.' => Tile::Ground,
+                    'S' => Tile::Start,
+                    _ => panic!("Unknown tile: {}", c),
+                };
+
+                (pos, tile)
+            })
+        })
+        .collect::<BTreeMap<Point, Tile>>();
+
+    grid
+}
+
+#[tracing::instrument]
+pub fn process(input: &str) -> miette::Result<u64, AocError> {
+    let grid = parse(input);
+    let start: &Point = grid
+        .iter()
+        .find(|(_, tile)| **tile == Tile::Start)
+        .map(|(pos, _)| pos)
+        .unwrap();
+
+    let start_connects: Vec<&Point> = grid
+        .iter()
+        .filter(|(_, tile)| match tile {
+            Tile::Vertical(pipe) => pipe.input == *start || pipe.output == *start,
+            Tile::Horizontal(pipe) => pipe.input == *start || pipe.output == *start,
+            Tile::NorthEast(pipe) => pipe.input == *start || pipe.output == *start,
+            Tile::NorthWest(pipe) => pipe.input == *start || pipe.output == *start,
+            Tile::SouthWest(pipe) => pipe.input == *start || pipe.output == *start,
+            Tile::SouteEast(pipe) => pipe.input == *start || pipe.output == *start,
+            _ => false,
+        })
+        .map(|(pos, _)| pos)
+        .collect();
+
+    let mut current = *start_connects.first().unwrap();
+    let mut prev = start;
+    let mut steps: u64 = 1;
+    while current != start {
+        let tile = grid.get(current).unwrap();
+        match tile {
+            Tile::Vertical(p)
+            | Tile::Horizontal(p)
+            | Tile::NorthEast(p)
+            | Tile::NorthWest(p)
+            | Tile::SouteEast(p)
+            | Tile::SouthWest(p) => {
+                if p.input == *prev {
+                    prev = current;
+                    current = &p.output;
+                } else {
+                    prev = current;
+                    current = &p.input;
+                }
+            }
+            _ => panic!("Unknown tile: {:?}", tile),
+        }
+
+        steps += 1;
+    }
+
+    Ok(steps / 2)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rstest::rstest;
+
+    #[test_log::test(rstest)]
+    #[case("test-input.txt", 4)]
+    #[case("test-input2.txt", 8)]
+    fn test_process(#[case] filename: &str, #[case] expected: usize) -> miette::Result<()> {
+        let input =
+            String::from_utf8_lossy(&std::fs::read(std::path::Path::new(filename)).unwrap())
+                .parse::<String>()
+                .unwrap();
+        assert_eq!(expected, process(&input)? as usize);
+        Ok(())
+    }
+}