10 rust

3 files changed, 84 insertions, 0 deletions

diff --git a/10/rust/Cargo.lock b/10/rust/Cargo.lock
new file mode 100644
index 0000000..b21cc6a
--- /dev/null
+++ b/10/rust/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "rust"
+version = "0.1.0"
diff --git a/10/rust/Cargo.toml b/10/rust/Cargo.toml
new file mode 100644
index 0000000..1ec6963
--- /dev/null
+++ b/10/rust/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "rust"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/10/rust/src/main.rs b/10/rust/src/main.rs
new file mode 100644
index 0000000..7c0c3fe
--- /dev/null
+++ b/10/rust/src/main.rs
@@ -0,0 +1,69 @@
+use std::io::BufRead;
+
+struct Grid(Vec<String>);
+
+impl Grid {
+    fn at(&self, x: isize, y: isize) -> char {
+        return self.0[y as usize].chars().nth(x as usize).unwrap();
+    }
+}
+
+fn main() {
+    let mut grid: Grid = Grid(vec![]);
+
+    for line in std::io::stdin().lock().lines() {
+        grid.0.push(line.unwrap());
+    }
+
+    let mut start_x = 0;
+    let mut start_y = 0;
+    'outer: for (y, line) in grid.0.iter().enumerate() {
+        for (x, c) in line.chars().enumerate() {
+            if c == 'S' {
+                start_x = x;
+                start_y = y;
+                break 'outer;
+            }
+        }
+    }
+    assert!(start_x != 0);
+    assert!(start_y != 0);
+
+    println!(
+        "{}",
+        traverse(&grid, start_x as isize, start_y as isize) / 2
+    );
+}
+
+fn traverse(grid: &Grid, start_x: isize, start_y: isize) -> usize {
+    let mut x = start_x;
+    let mut y = start_y;
+    let mut dir_x = 0isize;
+    let mut dir_y = 0isize;
+    let mut steps = 1;
+
+    if "-LF".contains(grid.at(x - 1, y)) {
+        dir_x = -1;
+    } else if "-J7".contains(grid.at(x + 1, y)) {
+        dir_x = 1;
+    } else if "|7F".contains(grid.at(x, y - 1)) {
+        dir_y = -1;
+    } else if "|JL".contains(grid.at(x, y + 1)) {
+        dir_y = 1;
+    } else {
+        panic!("no valid adjacent pipe found");
+    }
+
+    loop {
+        steps += 1;
+        x += dir_x;
+        y += dir_y;
+        match grid.at(x, y) {
+            '-' | '|' => (),
+            '7' | 'L' => (dir_x, dir_y) = (dir_y, dir_x),
+            'F' | 'J' => (dir_x, dir_y) = (-dir_y, -dir_x),
+            'S' => return steps,
+            _ => unreachable!(),
+        }
+    }
+}