day 10

README.md

@@ -34,6 +34,7 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 7](./src/bin/07.rs) | `487.3µs` | `862.0µs` |
 | [Day 8](./src/bin/08.rs) | `36.5µs` | `116.8µs` |
 | [Day 9](./src/bin/09.rs) | `80.1µs` | `258.4ms` |
+| [Day 10](./src/bin/10.rs) | `464.5µs` | `28.4µs` |
 
-**Total: 293.85ms**
+**Total: 294.35ms**
 <!--- benchmarking table --->

data/examples/10.txt

@@ -0,0 +1,8 @@
+89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732

src/bin/10.rs

@@ -0,0 +1,176 @@
+use std::{collections::HashSet, ops::Add};
+
+use itertools::Itertools;
+
+advent_of_code::solution!(10);
+
+#[derive(Debug, Eq, Hash, PartialEq, Clone, Copy)]
+struct Position(usize, usize);
+
+pub fn part_one(input: &str) -> Option<usize> {
+    let mut trailheads = vec![];
+
+    let map = input
+        .lines()
+        .enumerate()
+        .map(|(ydx, line)| {
+            line.chars()
+                .enumerate()
+                .map(|(xdx, ch)| {
+                    let num = ch.to_digit(10).unwrap_or(100);
+                    if num == 0 {
+                        trailheads.push((xdx, ydx));
+                    }
+                    num
+                })
+                .collect_vec()
+        })
+        .collect_vec();
+
+    let mut res = 0;
+    for th in trailheads {
+        let tmp = dfs_step(&map, Position(th.0, th.1), 0);
+        res += tmp.len();
+    }
+
+    Some(res)
+}
+
+fn dfs_step(map: &[Vec<u32>], current_pos: Position, current_val: u32) -> HashSet<Position> {
+    if current_val == 9 {
+        let mut set = HashSet::new();
+        set.insert(current_pos);
+        return set;
+    }
+
+    let mut result = HashSet::new();
+    // Up
+    if current_pos.1 > 0 && map[current_pos.1 - 1][current_pos.0] == current_val + 1 {
+        result.extend(dfs_step(
+            map,
+            Position(current_pos.0, current_pos.1 - 1),
+            current_val + 1,
+        ));
+    };
+
+    // Righht
+    if current_pos.0 < map[0].len() - 1 && map[current_pos.1][current_pos.0 + 1] == current_val + 1
+    {
+        result.extend(dfs_step(
+            map,
+            Position(current_pos.0 + 1, current_pos.1),
+            current_val + 1,
+        ));
+    };
+
+    // Down
+    if current_pos.1 < map.len() - 1 && map[current_pos.1 + 1][current_pos.0] == current_val + 1 {
+        result.extend(dfs_step(
+            map,
+            Position(current_pos.0, current_pos.1 + 1),
+            current_val + 1,
+        ));
+    };
+
+    // Left
+    if current_pos.0 > 0 && map[current_pos.1][current_pos.0 - 1] == current_val + 1 {
+        result.extend(dfs_step(
+            map,
+            Position(current_pos.0 - 1, current_pos.1),
+            current_val + 1,
+        ));
+    };
+
+    result
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let mut trailheads = vec![];
+
+    let map = input
+        .lines()
+        .enumerate()
+        .map(|(ydx, line)| {
+            line.chars()
+                .enumerate()
+                .map(|(xdx, ch)| {
+                    let num = ch.to_digit(10).unwrap_or(100);
+                    if num == 0 {
+                        trailheads.push((xdx, ydx));
+                    }
+                    num
+                })
+                .collect_vec()
+        })
+        .collect_vec();
+
+    let mut res = 0;
+    for th in trailheads {
+        res += dfs_step_2(&map, Position(th.0, th.1), 0);
+    }
+
+    Some(res)
+}
+
+fn dfs_step_2(map: &[Vec<u32>], current_pos: Position, current_val: u32) -> u32 {
+    if current_val == 9 {
+        return 1;
+    }
+
+    let mut result: u32 = 0;
+    // Up
+    if current_pos.1 > 0 && map[current_pos.1 - 1][current_pos.0] == current_val + 1 {
+        result = result.add(dfs_step_2(
+            map,
+            Position(current_pos.0, current_pos.1 - 1),
+            current_val + 1,
+        ));
+    };
+
+    // Righht
+    if current_pos.0 < map[0].len() - 1 && map[current_pos.1][current_pos.0 + 1] == current_val + 1
+    {
+        result = result.add(dfs_step_2(
+            map,
+            Position(current_pos.0 + 1, current_pos.1),
+            current_val + 1,
+        ));
+    };
+
+    // Down
+    if current_pos.1 < map.len() - 1 && map[current_pos.1 + 1][current_pos.0] == current_val + 1 {
+        result = result.add(dfs_step_2(
+            map,
+            Position(current_pos.0, current_pos.1 + 1),
+            current_val + 1,
+        ));
+    };
+
+    // Left
+    if current_pos.0 > 0 && map[current_pos.1][current_pos.0 - 1] == current_val + 1 {
+        result = result.add(dfs_step_2(
+            map,
+            Position(current_pos.0 - 1, current_pos.1),
+            current_val + 1,
+        ));
+    };
+
+    result
+}
+
+#[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, None);
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}