diff --git a/data/examples/10.txt b/data/examples/10.txt
new file mode 100644
index 0000000..cada9b3
--- /dev/null
+++ b/data/examples/10.txt
@@ -0,0 +1,8 @@
+89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732
diff --git a/src/bin/10.rs b/src/bin/10.rs
new file mode 100644
index 0000000..16e0c4b
--- /dev/null
+++ b/src/bin/10.rs
@@ -0,0 +1,165 @@
+advent_of_code::solution!(10);
+
+use std::iter::successors;
+
+#[derive(Debug, Clone, PartialOrd, Ord, PartialEq, Eq)]
+struct Pos {
+    x: usize,
+    y: usize,
+}
+
+#[derive(Debug)]
+struct Topo {
+    map: Vec<Vec<u8>>,
+    max: Pos,
+}
+
+impl Topo {
+    fn init(input: &str) -> Result<Self, ()> {
+        let map: Vec<Vec<u8>> = input
+            .strip_suffix("\n")
+            .unwrap_or(input)
+            .lines()
+            .map(|l| {
+                l.chars()
+                    .flat_map(|c| c.to_digit(10u32))
+                    .map(|d| d as u8)
+                    .collect()
+            })
+            .collect();
+        let max = Pos {
+            x: map[0].len(),
+            y: map.len(),
+        };
+        Ok(Self { map, max })
+    }
+
+    fn get_trailheads(&self) -> Vec<Pos> {
+        self.map
+            .clone()
+            .into_iter()
+            .enumerate()
+            .flat_map(|(y, l)| {
+                l.into_iter()
+                    .enumerate()
+                    .map(move |(x, c)| (Pos { x, y }, c))
+            })
+            .filter_map(|(p, c)| if c == 0 { Some(p) } else { None })
+            .collect()
+    }
+
+    fn get_neighbors(&self, p: &Pos) -> Vec<(Pos, u8)> {
+        let mut res: Vec<(Pos, u8)> = Vec::new();
+        if p.x > 0 {
+            let x = p.x - 1;
+            let y = p.y;
+            res.push((Pos { x, y }, self.map[y][x]));
+        }
+        if p.y > 0 {
+            let x = p.x;
+            let y = p.y - 1;
+            res.push((Pos { x, y }, self.map[y][x]));
+        }
+        if p.x < self.max.x - 1 {
+            let x = p.x + 1;
+            let y = p.y;
+            res.push((Pos { x, y }, self.map[y][x]));
+        }
+        if p.y < self.max.y - 1 {
+            let x = p.x;
+            let y = p.y + 1;
+            res.push((Pos { x, y }, self.map[y][x]));
+        }
+        res
+    }
+
+    fn get_successors(&self, p: (Pos, u8)) -> Vec<(Pos, u8)> {
+        self.get_neighbors(&p.0)
+            .into_iter()
+            .filter_map(|(p2, d2)| if d2 == p.1 + 1 { Some((p2, d2)) } else { None })
+            .collect()
+    }
+
+    fn dfs(&self, p: (Pos, u8), path: &mut Vec<(Pos, u8)>, all_routes: &mut Vec<Vec<(Pos, u8)>>) {
+        if p.1 == 9 {
+            all_routes.push(path.clone());
+            return;
+        }
+
+        for n in self.get_successors(p) {
+            path.push(n.clone());
+            self.dfs(n, path, all_routes);
+            path.pop();
+        }
+    }
+}
+
+fn print_route(route: Vec<(Pos, u8)>, max: &Pos) {
+    println!("==========");
+    for y in 0..max.y {
+        print!("|");
+        for x in 0..max.x {
+            let mut found = false;
+            for r in &route {
+                if r.0.x == x && r.0.y == y {
+                    found = true;
+                    print!("{}", r.1);
+                }
+            }
+            if !found {
+                print!(" ");
+            }
+        }
+        println!("|");
+    }
+    println!("==========");
+}
+
+pub fn part_one(input: &str) -> Option<usize> {
+    let topo = Topo::init(input).ok()?;
+    let ths = topo.get_trailheads();
+    let mut score = 0;
+
+    for th in ths {
+        let mut all_routes: Vec<Vec<(Pos, u8)>> = Vec::new();
+        let mut path: Vec<(Pos, u8)> = vec![(th.clone(), 0)];
+        topo.dfs((th, 0), &mut path, &mut all_routes);
+        let mut ends = all_routes
+            .into_iter()
+            .map(|v| v.last().unwrap().0.clone())
+            .collect::<Vec<Pos>>();
+        ends.sort();
+        ends.dedup();
+        score += ends.len();
+    }
+    Some(score)
+}
+
+pub fn part_two(input: &str) -> Option<usize> {
+    let topo = Topo::init(input).ok()?;
+    let ths = topo.get_trailheads();
+    let mut all_routes: Vec<Vec<(Pos, u8)>> = Vec::new();
+
+    for th in ths {
+        let mut path: Vec<(Pos, u8)> = vec![(th.clone(), 0)];
+        topo.dfs((th, 0), &mut path, &mut all_routes);
+    }
+    Some(all_routes.len())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(36));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(81));
+    }
+}