diff --git a/day12/src/main.rs b/day12/src/main.rs
index 13cbc8a..945a536 100644
--- a/day12/src/main.rs
+++ b/day12/src/main.rs
@@ -3,7 +3,7 @@ use aoc_shared::grid::Grid as BaseGrid;
 use aoc_shared::impl_grid_newtype;
 
 #[derive(Debug)]
-struct Grid<T>(BaseGrid<T>);
+pub struct Grid<T>(BaseGrid<T>);
 impl_grid_newtype!(Grid, BaseGrid<char>, char);
 
 impl Grid<char> {
@@ -23,56 +23,124 @@ impl Grid<char> {
     fn find_pos(&self, value: char) -> Option<usize> {
         self.vec.iter().position(|item| *item == value)
     }
+}
 
-    fn find_start_and_end(&self) -> (usize, usize) {
-        let start = self.vec.iter().position(|item| *item == 'S').unwrap();
-        let end = self.vec.iter().position(|item| *item == 'E').unwrap();
+// ----------------------------------------------------------------------------
 
-        (start, end)
+#[derive(Debug, Default, Clone)]
+pub struct Node {
+    idx: usize,
+    parents: Vec<usize>,
+    children: Option<Vec<Box<Node>>>,
+}
+
+impl Node {
+    pub fn new(idx: usize) -> Self {
+        Node {
+            idx,
+            ..Node::default()
+        }
+    }
+
+    pub fn add_child(&mut self, value: usize) -> &mut Self {
+        let mut child = Node::new(value);
+        child.parents.append(&mut self.parents.clone());
+        child.parents.push(self.idx);
+
+        self.append(child);
+
+        self.children
+            .as_mut()
+            .expect("There should be a Vec here!")
+            .last_mut()
+            .expect("There should be a Box here!")
+    }
+
+    fn append(&mut self, node: Node) -> &mut Self {
+        match &mut self.children {
+            Some(c) => {
+                c.push(Box::new(node));
+            }
+            None => self.children = Some(vec![Box::new(node)]),
+        };
+
+        self
+    }
+
+    fn is_leaf(&self) -> bool {
+        self.children.is_none()
+    }
+
+    pub fn contains(&self, value: usize) -> bool {
+        if self.idx == value {
+            return true;
+        }
+
+        return self.parents.contains(&value);
+    }
+
+    pub fn get_leaves(&self) -> Vec<Node> {
+        if self.is_leaf() {
+            return vec![self.to_owned()];
+        }
+
+        let mut leaves = Vec::new();
+
+        let children = self
+            .children
+            .as_ref()
+            .unwrap()
+            .iter()
+            .map(|boxed| boxed.as_ref());
+
+        for child in children {
+            let mut child_leaves = child.get_leaves();
+            leaves.append(&mut child_leaves);
+        }
+
+        leaves
+    }
+
+    pub fn get_len(&self) -> usize {
+        self.parents.len()
     }
 }
 
 // ----------------------------------------------------------------------------
 
 #[derive(Debug)]
-struct Pathfinder {
+pub struct Pathfinder {
     current_elevation: char,
-    current_idx: usize,
     start_idx: usize,
     end_idx: usize,
     grid: Grid<char>,
-    steps: Vec<Direction>,
+    tree: Node,
 }
 
 impl Pathfinder {
     pub fn from_file_str(file_str: &str) -> Self {
         let mut pf = Pathfinder {
             current_elevation: 'a',
-            current_idx: 0,
             start_idx: 0,
             end_idx: 0,
             grid: Grid::from_file_str(file_str),
-            steps: Vec::new(),
+            tree: Node::default(),
         };
         pf.go_to_start();
 
         pf
     }
 
-    fn find_start_and_end(&self) -> (usize, usize) {
-        (self.start_idx, self.end_idx)
-    }
-
     fn go_to_start(&mut self) {
         let start = self.grid.find_pos('S').unwrap();
         let end = self.grid.find_pos('E').unwrap();
 
-        self.current_idx = start;
         self.start_idx = start;
         self.end_idx = end;
         self.current_elevation = 'a';
         self.grid.vec[start] = 'a';
         self.grid.vec[end] = 'z';
+        self.tree.idx = start;
     }
 
     fn get_index_for_move(&self, from: usize, dir: Direction) -> Option<usize> {
@@ -112,48 +180,97 @@ impl Pathfinder {
         Some(self.grid.xy_idx(x, y))
     }
 
-    fn is_valid_move(&self, start: usize, dir: Direction) -> bool {
-        if let Some(end) = self.get_index_for_move(start, dir) {
-            // Is the item within the grid?
-            let start_char = self.grid.get(start);
-            let end_char = self.grid.get(end);
-            if start_char.is_none() || end_char.is_none() {
-                return false;
-            }
+    fn is_valid_move(&self, start: usize, end: usize) -> bool {
+        // Is the item within the grid?
+        let start_char = self.grid.get(start);
+        let end_char = self.grid.get(end);
+        if start_char.is_none() || end_char.is_none() {
+            return false;
+        }
 
-            // Is the elevation change 0 or 1?
-            let start_char = *start_char.unwrap();
-            let end_char = *end_char.unwrap();
-            println!("start, end: {}, {}", start_char, end_char);
-            let diff = end_char.to_digit(26).unwrap() - start_char.to_digit(26).unwrap();
-            if diff > 1 || end_char < start_char {
-                return false;
-            }
+        // Is the elevation change 0 or 1?
+        let start_char = *start_char.unwrap();
+        let end_char = *end_char.unwrap();
+        let start_char = start_char
+            .to_digit(36)
+            .expect(&format!("Should be a digit: {}", start_char)) as i32;
+        let end_char = end_char
+            .to_digit(36)
+            .expect(&format!("Should be a digit: {}", end_char)) as i32;
+        let diff = end_char - start_char;
+        if diff > 1 || diff < 0 || end_char < start_char {
+            return false;
+        }
 
-            let (start_x, start_y) = self.grid.idx_xy(start);
-            let (end_x, end_y) = self.grid.idx_xy(end);
-            let x_diff = usize::abs_diff(end_x,  start_x);
-            let y_diff = usize::abs_diff(end_y, start_y);
+        let (start_x, start_y) = self.grid.idx_xy(start);
+        let (end_x, end_y) = self.grid.idx_xy(end);
+        let x_diff = usize::abs_diff(end_x, start_x);
+        let y_diff = usize::abs_diff(end_y, start_y);
 
-            // Have we moved 0 or 1 in a cardinal direction?
-            return match (x_diff, y_diff) {
-                (0, 0) | (0, 1) | (1,0) => true,
-                _ => false,
-            };
-        };
-
-        false
+        // Have we moved 0 or 1 in a cardinal direction?
+        match (x_diff, y_diff) {
+            (0, 0) | (0, 1) | (1, 0) => true,
+            _ => false,
+        }
     }
 
     fn find_valid_moves(&self, start: usize) -> Vec<usize> {
-        [Direction::Up, Direction::Down, Direction::Left, Direction::Right]
+        [
+            Direction::Up,
+            Direction::Down,
+            Direction::Left,
+            Direction::Right,
+        ]
+        .into_iter()
+        .map(|d| self.get_index_for_move(start, d))
+        .filter(|m| m.is_some())
+        .map(|m| m.unwrap())
+        .filter(|m| self.is_valid_move(start, *m))
+        .collect()
+    }
+
+    fn add_children(&mut self, node: &mut Node, idx: usize) {
+        let possible_moves = self.find_valid_moves(idx);
+
+        for m in possible_moves {
+            if node.contains(m) {
+                continue;
+            }
+
+            let mut n = node.add_child(m);
+            if m != self.end_idx {
+                self.add_children(&mut n, m);
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn build_tree(&mut self) {
+        let mut tree = { self.tree.clone() };
+        let idx = { self.start_idx };
+
+        self.add_children(&mut tree, idx);
+        self.tree = tree;
+    }
+
+    fn get_paths(&self) -> Vec<Node> {
+        self.tree
+            .get_leaves()
             .into_iter()
-            .filter(|d| self.is_valid_move(start, *d))
-            .map(|d| self.get_index_for_move(start, d))
-            .filter(|m| m.is_some())
-            .map(|m| m.unwrap())
+            .filter(|n| n.idx == self.end_idx)
             .collect()
     }
+
+    pub fn find_shortest_path(&mut self) -> Node {
+        self.build_tree();
+
+        self.get_paths()
+            .iter()
+            .min_by(|a, b| a.get_len().cmp(&b.get_len()))
+            .unwrap()
+            .to_owned()
+    }
 }
 
 // ----------------------------------------------------------------------------
@@ -161,6 +278,9 @@ impl Pathfinder {
 fn main() {
     let file_str = include_str!("input.txt");
     let mut finder = Pathfinder::from_file_str(file_str);
+    let shortest_path = finder.find_shortest_path();
+
+    println!("Part 1: Fewest steps: {}", shortest_path.get_len());
 }
 
 #[cfg(test)]
@@ -171,20 +291,22 @@ mod tests {
         include_str!("test-input.txt")
     }
 
-    #[test]
-    fn get_start_end() {
-        let finder = Pathfinder::from_file_str(get_test_data());
-        let (start, end) = finder.find_start_and_end();
-
-        assert_eq!((start, end), (0, 21));
+    fn get_finder() -> Pathfinder {
+        Pathfinder::from_file_str(get_test_data())
     }
 
     #[test]
     fn find_valid_moves() {
-        let finder = Pathfinder::from_file_str(get_test_data());
-        let (start, end) = finder.find_start_and_end();
+        let finder = get_finder();
 
-        assert_eq!(finder.find_valid_moves(start), vec![8, 1]);
-        assert_eq!(finder.find_valid_moves(8), vec![16, 9]);
+        assert_eq!(finder.find_valid_moves(finder.start_idx), vec![8, 1]);
+        assert_eq!(finder.find_valid_moves(8), vec![0, 16, 9]);
+    }
+
+    #[test]
+    fn find_shortest_path() {
+        let shortest = get_finder().find_shortest_path();
+
+        assert_eq!(shortest.get_len(), 31);
     }
 }