diff --git a/Cargo.lock b/Cargo.lock
index 919a337..31a8806 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,10 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "aoc_utils"
+version = "0.1.0"
+
 [[package]]
 name = "d01t1"
 version = "0.1.0"
@@ -73,3 +77,14 @@ version = "0.1.0"
 [[package]]
 name = "d09t2"
 version = "0.1.0"
+
+[[package]]
+name = "d10t1"
+version = "0.1.0"
+dependencies = [
+ "aoc_utils",
+]
+
+[[package]]
+name = "d10t2"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 29a8e05..0606f18 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,6 +2,7 @@
 
 resolver = "2"
 members = [
+    "aoc_utils",
     "d01t1",
     "d01t2",
     "d02t1",
@@ -20,4 +21,6 @@ members = [
     "d08t2",
     "d09t1",
     "d09t2",
+    "d10t1",
+    "d10t2",
 ]
diff --git a/aoc_utils/Cargo.toml b/aoc_utils/Cargo.toml
new file mode 100644
index 0000000..51b4ff0
--- /dev/null
+++ b/aoc_utils/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "aoc_utils"
+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/aoc_utils/src/lib.rs b/aoc_utils/src/lib.rs
new file mode 100644
index 0000000..d9b9d44
--- /dev/null
+++ b/aoc_utils/src/lib.rs
@@ -0,0 +1,33 @@
+#[must_use]
+pub fn dec_if_pos(input: usize) -> usize {
+    if input > 0 {
+        input - 1
+    } else {
+        input
+    }
+}
+
+#[must_use]
+pub fn inc_if_lt(input: usize, max: usize) -> usize {
+    if input < max {
+        input + 1
+    } else {
+        input
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+
+    #[test]
+    fn test_dec() {
+        assert_eq!(dec_if_pos(0), 0);
+        assert_eq!(dec_if_pos(1), 0);
+    }
+    #[test]
+    fn test_inc() {
+        assert_eq!(inc_if_lt(3, 3), 3);
+        assert_eq!(inc_if_lt(2, 3), 3);
+    }
+}
diff --git a/d10t1/Cargo.toml b/d10t1/Cargo.toml
new file mode 100644
index 0000000..b535155
--- /dev/null
+++ b/d10t1/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "d10t1"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aoc_utils = { path = "../aoc_utils" }
diff --git a/d10t1/demo_input.txt b/d10t1/demo_input.txt
new file mode 100644
index 0000000..3c00cf2
--- /dev/null
+++ b/d10t1/demo_input.txt
@@ -0,0 +1,5 @@
+..F7.
+.FJ|.
+SJ.L7
+|F--J
+LJ...
\ No newline at end of file
diff --git a/d10t1/src/main.rs b/d10t1/src/main.rs
new file mode 100644
index 0000000..ee68e4d
--- /dev/null
+++ b/d10t1/src/main.rs
@@ -0,0 +1,94 @@
+use std::fs::read_to_string;
+
+fn main() {
+    let input = read_to_string("input.txt").unwrap();
+    println!("d10t1: {}", d10t1(&input));
+}
+
+pub fn d10t1(input: &str) -> isize {
+    let field = input
+        .lines()
+        .map(str::chars)
+        .map(std::iter::Iterator::collect::<Vec<_>>)
+        .collect::<Vec<_>>();
+    let mut distances = vec![vec![-1; field[0].len()]; field.len()];
+    let mut starting_position: Option<(usize, usize)> = None;
+    for (y, line) in field.iter().enumerate() {
+        for (x, field) in line.iter().enumerate() {
+            if *field == 'S' {
+                starting_position = Some((x, y));
+                distances[y][x] = 0;
+            }
+        }
+    }
+    let starting_position = starting_position.unwrap();
+    traverse(&mut distances, &field, starting_position);
+    *distances.iter().flat_map(|a| a.iter()).max().unwrap()
+}
+
+fn traverse(distances: &mut [Vec<isize>], field: &Vec<Vec<char>>, position: (usize, usize)) {
+    let height = field.len() - 1;
+    let width = field[0].len() - 1;
+    let mut locations_to_check = vec![position];
+    while let Some((x, y)) = locations_to_check.pop() {
+        let starting_value = distances[y][x];
+        assert_ne!(
+            starting_value, -1,
+            "traverse should only be called on locations that have already been set."
+        );
+        if x != 0 && (distances[y][x - 1] == -1 || distances[y][x - 1] > starting_value) {
+            match (field[y][x], field[y][x - 1]) {
+                ('|' | 'L' | 'F', _) | (_, '.' | '|' | 'J' | '7') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('-' | 'J' | '7' | 'S', '-' | 'L' | 'F') => {
+                    distances[y][x - 1] = starting_value + 1;
+                    locations_to_check.push((x - 1, y));
+                }
+                _ => unimplemented!(),
+            }
+        }
+        if x < width && (distances[y][x + 1] == -1 || distances[y][x + 1] > starting_value) {
+            match (field[y][x], field[y][x + 1]) {
+                ('|' | 'J' | '7', _) | (_, '.' | '|' | 'L' | 'F') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('-' | 'L' | 'F' | 'S', '-' | 'J' | '7') => {
+                    distances[y][x + 1] = starting_value + 1;
+                    locations_to_check.push((x + 1, y));
+                }
+                _ => unimplemented!(),
+            }
+        }
+        if y != 0 && (distances[y - 1][x] == -1 || distances[y - 1][x] > starting_value) {
+            match (field[y][x], field[y - 1][x]) {
+                ('-' | 'F' | '7', _) | (_, '.' | '-' | 'J' | 'L') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('|' | 'L' | 'J' | 'S', '|' | 'F' | '7') => {
+                    distances[y - 1][x] = starting_value + 1;
+                    locations_to_check.push((x, y - 1));
+                }
+                _ => unimplemented!(),
+            }
+        }
+        if y < height && (distances[y + 1][x] == -1 || distances[y + 1][x] > starting_value) {
+            match (field[y][x], field[y + 1][x]) {
+                ('-' | 'L' | 'J', _) | (_, '.' | '-' | '7' | 'F') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('|' | 'F' | '7' | 'S', '|' | 'L' | 'J') => {
+                    distances[y + 1][x] = starting_value + 1;
+                    locations_to_check.push((x, y + 1));
+                }
+                _ => unimplemented!(),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_d10t1() {
+        let input = include_str!("../demo_input.txt");
+        assert_eq!(d10t1(input), 8);
+    }
+}
diff --git a/d10t2/Cargo.toml b/d10t2/Cargo.toml
new file mode 100644
index 0000000..4af3ee2
--- /dev/null
+++ b/d10t2/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "d10t2"
+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/d10t2/demo_input.txt b/d10t2/demo_input.txt
new file mode 100644
index 0000000..fbc0300
--- /dev/null
+++ b/d10t2/demo_input.txt
@@ -0,0 +1,10 @@
+FF7FSF7F7F7F7F7F---7
+L|LJ||||||||||||F--J
+FL-7LJLJ||||||LJL-77
+F--JF--7||LJLJ7F7FJ-
+L---JF-JLJ.||-FJLJJ7
+|F|F-JF---7F7-L7L|7|
+|FFJF7L7F-JF7|JL---7
+7-L-JL7||F7|L7F-7F7|
+L.L7LFJ|||||FJL7||LJ
+L7JLJL-JLJLJL--JLJ.L
\ No newline at end of file
diff --git a/d10t2/demo_input_2.txt b/d10t2/demo_input_2.txt
new file mode 100644
index 0000000..2e5dcbb
--- /dev/null
+++ b/d10t2/demo_input_2.txt
@@ -0,0 +1,10 @@
+.F----7F7F7F7F-7....
+.|F--7||||||||FJ....
+.||.FJ||||||||L7....
+FJL7L7LJLJ||LJ.L-7..
+L--J.L7...LJS7F-7L7.
+....F-J..F7FJ|L7L7L7
+....L7.F7||L7|.L7L7|
+.....|FJLJ|FJ|F7|.LJ
+....FJL-7.||.||||...
+....L---J.LJ.LJLJ...
\ No newline at end of file
diff --git a/d10t2/demo_input_3.txt b/d10t2/demo_input_3.txt
new file mode 100644
index 0000000..6933a28
--- /dev/null
+++ b/d10t2/demo_input_3.txt
@@ -0,0 +1,9 @@
+...........
+.S-------7.
+.|F-----7|.
+.||.....||.
+.||.....||.
+.|L-7.F-J|.
+.|..|.|..|.
+.L--J.L--J.
+...........
\ No newline at end of file
diff --git a/d10t2/src/main.rs b/d10t2/src/main.rs
new file mode 100644
index 0000000..69cf0a5
--- /dev/null
+++ b/d10t2/src/main.rs
@@ -0,0 +1,191 @@
+use std::fs::read_to_string;
+
+fn main() {
+    let input = read_to_string("input.txt").unwrap();
+    println!("d10t2: {}", d10t2(&input));
+}
+
+pub fn d10t2(input: &str) -> usize {
+    let mut field = input
+        .lines()
+        .map(str::chars)
+        .map(std::iter::Iterator::collect::<Vec<_>>)
+        .collect::<Vec<_>>();
+    let mut distances = vec![vec![-1; field[0].len()]; field.len()];
+    let starting_position = field
+        .iter()
+        .enumerate()
+        .flat_map(|(y, line)| line.iter().enumerate().map(move |(x, c)| (x, y, c)))
+        .find(|&(_x, _y, c)| *c == 'S')
+        .map(|(x, y, _c)| (x, y))
+        .unwrap();
+    distances[starting_position.1][starting_position.0] = 0;
+    traverse(&mut distances, &mut field, starting_position);
+    get_enclosed(&distances, &field)
+}
+
+fn get_effective_char_for_start(distances: &[Vec<isize>]) -> char {
+    let starting_position = distances
+        .iter()
+        .enumerate()
+        .flat_map(|(y, line)| line.iter().enumerate().map(move |(x, c)| (x, y, c)))
+        .find(|&(_x, _y, c)| *c == 0)
+        .map(|(x, y, _c)| (x, y))
+        .unwrap();
+    let bounds = (distances[0].len() - 1, distances.len() - 1);
+    let (x, y) = starting_position;
+    let top = if y == 0 {
+        false
+    } else {
+        distances[y - 1][x] == 1
+    };
+    let bottom = if y == bounds.1 {
+        false
+    } else {
+        distances[y + 1][x] == 1
+    };
+    let left = if x == 0 {
+        false
+    } else {
+        distances[y][x - 1] == 1
+    };
+    let right = if x == bounds.0 {
+        false
+    } else {
+        distances[y][x + 1] == 1
+    };
+    match (top, bottom, left, right) {
+        (true, true, false, false) => '|',
+        (false, false, true, true) => '-',
+        (true, false, true, false) => 'J',
+        (true, false, false, true) => 'L',
+        (false, true, true, false) => '7',
+        (false, true, false, true) => 'F',
+        _ => unreachable!(),
+    }
+}
+
+fn get_enclosed(distances: &[Vec<isize>], field: &[Vec<char>]) -> usize {
+    let mut result = 0;
+    let s_char = get_effective_char_for_start(distances);
+    let unique_y_changes = |x: usize, until: usize| -> usize {
+        field[0..until]
+            .iter()
+            .enumerate()
+            .filter(|(idx, _)| distances[*idx][x] != -1)
+            .map(|(_, s)| s[x])
+            .collect::<String>()
+            .replace('S', s_char.to_string().as_str())
+            .replace('|', "")
+            .replace("FL", "")
+            .replace("FJ", "-")
+            .replace("7L", "-")
+            .replace("7J", "")
+            .replace('.', "")
+            .len()
+    };
+    let unique_x_changes = |y: usize, until: usize| -> usize {
+        field[y][0..until]
+            .iter()
+            .enumerate()
+            .filter(|(idx, _)| distances[y][*idx] != -1)
+            .map(|(_, c)| *c)
+            .collect::<String>()
+            .replace('S', s_char.to_string().as_str())
+            .replace('-', "")
+            .replace("F7", "")
+            .replace("FJ", "|")
+            .replace("L7", "|")
+            .replace("LJ", "")
+            .replace('.', "")
+            .len()
+    };
+    for (y, line) in distances.iter().enumerate() {
+        for (x, _d) in line.iter().enumerate() {
+            if distances[y][x] == -1 {
+                if unique_x_changes(y, x) % 2 == 1 && unique_y_changes(x, y) % 2 == 1 {
+                    result += 1;
+                }
+            }
+        }
+    }
+
+    result
+}
+
+fn traverse(distances: &mut [Vec<isize>], field: &mut Vec<Vec<char>>, position: (usize, usize)) {
+    let height = field.len() - 1;
+    let width = field[0].len() - 1;
+    let mut locations_to_check = vec![position];
+    while let Some((x, y)) = locations_to_check.pop() {
+        let starting_value = distances[y][x];
+        assert_ne!(
+            starting_value, -1,
+            "traverse should only be called on locations that have already been set."
+        );
+        if x != 0 && (distances[y][x - 1] == -1 || distances[y][x - 1] > starting_value) {
+            match (field[y][x], field[y][x - 1]) {
+                ('|' | 'L' | 'F', _) | (_, '.' | '|' | 'J' | '7') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('-' | 'J' | '7' | 'S', '-' | 'L' | 'F') => {
+                    distances[y][x - 1] = starting_value + 1;
+                    locations_to_check.push((x - 1, y));
+                }
+                _ => unimplemented!(),
+            }
+        }
+        if x < width && (distances[y][x + 1] == -1 || distances[y][x + 1] > starting_value) {
+            match (field[y][x], field[y][x + 1]) {
+                ('|' | 'J' | '7', _) | (_, '.' | '|' | 'L' | 'F') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('-' | 'L' | 'F' | 'S', '-' | 'J' | '7') => {
+                    distances[y][x + 1] = starting_value + 1;
+                    locations_to_check.push((x + 1, y));
+                }
+                _ => unimplemented!(),
+            }
+        }
+        if y != 0 && (distances[y - 1][x] == -1 || distances[y - 1][x] > starting_value) {
+            match (field[y][x], field[y - 1][x]) {
+                ('-' | 'F' | '7', _) | (_, '.' | '-' | 'J' | 'L') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('|' | 'L' | 'J' | 'S', '|' | 'F' | '7') => {
+                    distances[y - 1][x] = starting_value + 1;
+                    locations_to_check.push((x, y - 1));
+                }
+                _ => unimplemented!(),
+            }
+        }
+        if y < height && (distances[y + 1][x] == -1 || distances[y + 1][x] > starting_value) {
+            match (field[y][x], field[y + 1][x]) {
+                ('-' | 'L' | 'J', _) | (_, '.' | '-' | '7' | 'F') => {}
+                ('.', _) | (_, 'S') => unreachable!(),
+                ('|' | 'F' | '7' | 'S', '|' | 'L' | 'J') => {
+                    distances[y + 1][x] = starting_value + 1;
+                    locations_to_check.push((x, y + 1));
+                }
+                _ => unimplemented!(),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_d10t2() {
+        let input = include_str!("../demo_input.txt");
+        assert_eq!(d10t2(input), 10);
+    }
+    #[test]
+    fn test_d10t2_2() {
+        let input = include_str!("../demo_input_2.txt");
+        assert_eq!(d10t2(input), 8);
+    }
+    #[test]
+    fn test_d10t2_3() {
+        let input = include_str!("../demo_input_3.txt");
+        assert_eq!(d10t2(input), 4);
+    }
+}