day 16 pt2

data/examples/16-2.txt

@@ -0,0 +1,17 @@
+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################

data/examples/16.txt

@@ -0,0 +1,15 @@
+###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############

src/bin/16.rs

@@ -1,11 +1,115 @@
+use std::u32::MAX;
+
+use itertools::Itertools;
+
 advent_of_code::solution!(16);
 
+#[derive(Debug)]
+#[derive(PartialEq)]
+enum TileObject {
+    Start,
+    End,
+    Empty,
+    Wall
+}
+
+fn get_tile_object(c: char) -> TileObject {
+    match c {
+        '.' => TileObject::Empty,
+        '#' => TileObject::Wall,
+        'S' => TileObject::Start,
+        'E' => TileObject::End,
+        _ => panic!()
+    }
+}
+
+struct Cost {
+    up: u32,
+    down: u32,
+    left: u32,
+    right: u32,
+}
+
 pub fn part_one(input: &str) -> Option<u32> {
+    let grid = input.lines().map(|l| {
+        l.chars().map(|c| get_tile_object(c)).collect_vec()
+    }).collect_vec();
+
+    let grid_height = grid.len();
+    let grid_width = grid[0].len();
+
+    let start_pos = grid.iter().enumerate().find_map(|(row_idx, row)| {
+        row.iter().enumerate().find_map(|(col_idx, t)| if *t == TileObject::Start { Some((row_idx, col_idx)) } else { None })
+    }).unwrap();
+
+    let mut score_card: Vec<Vec<Option<u32>>> = vec![vec![None; grid_width]; grid_height];
+
+    // From the starting position facing EAST
+    score_card[start_pos.0][start_pos.1] = Some(0);
+    explore(&grid, &mut score_card, start_pos, Cost { up: 1001, down: 1001, left: MAX, right: 1 });
+
+    let end_pos = grid.iter().enumerate().find_map(|(row_idx, row)| {
+        row.iter().enumerate().find_map(|(col_idx, t)| if *t == TileObject::End { Some((row_idx, col_idx)) } else { None })
+    }).unwrap();
+
+    let end_score = score_card[end_pos.0][end_pos.1].unwrap_or(0);
+    Some(end_score)
+}
+
+pub fn part_two(_input: &str) -> Option<u32> {
     None
 }
 
-pub fn part_two(input: &str) -> Option<u32> {
-    None
+fn explore(grid: &Vec<Vec<TileObject>>, score_card: &mut Vec<Vec<Option<u32>>>, pos: (usize, usize), move_cost: Cost) {
+    if grid[pos.0][pos.1] == TileObject::Wall { return; }
+
+    let grid_height = grid.len();
+    let grid_width = grid[0].len();
+
+    let pos_score = score_card[pos.0][pos.1].unwrap();
+
+    let get_step = |row_idx, col_idx| -> Option<(usize, usize)> {
+        if !(0..grid_height as isize).contains(&row_idx) || !(0..grid_width as isize).contains(&col_idx) { return None }
+        else if grid[row_idx as usize][col_idx as usize] == TileObject::Wall { return None }
+        else { return Some((row_idx as usize, col_idx as usize)) }
+    };
+
+    // UP
+    if let Some(step) = get_step(pos.0 as isize - 1, pos.1 as isize) {
+        let next_cost = score_card[step.0][step.1];
+        if move_cost.up != MAX && (Option::is_none(&next_cost) || next_cost.unwrap() > pos_score + move_cost.up) {
+            score_card[step.0][step.1] = Some(pos_score + move_cost.up);
+            explore(grid, score_card, step, Cost { up: 1, down: MAX, left: 1001, right: 1001 });
+        }
+    }
+
+    // DOWN
+    if let Some(step) = get_step(pos.0 as isize + 1, pos.1 as isize) {
+        let next_cost = score_card[step.0][step.1];
+        if move_cost.down != MAX && (Option::is_none(&next_cost) || next_cost.unwrap() > pos_score + move_cost.down) {
+            score_card[step.0][step.1] = Some(pos_score + move_cost.down);
+            explore(grid, score_card, step, Cost { up: MAX, down: 1, left: 1001, right: 1001 });
+        }
+    }
+
+    // LEFT
+    if let Some(step) = get_step(pos.0 as isize, pos.1 as isize - 1) {
+        let next_cost = score_card[step.0][step.1];
+        if move_cost.left != MAX && (Option::is_none(&next_cost) || next_cost.unwrap() > pos_score + move_cost.left) {
+            score_card[step.0][step.1] = Some(pos_score + move_cost.left);
+            explore(grid, score_card, step, Cost { up: 1001, down: 1001, left: 1, right: MAX });
+        }
+    }
+
+    // RIGHT
+    if let Some(step) = get_step(pos.0 as isize, pos.1 as isize + 1) {
+        let next_cost = score_card[step.0][step.1];
+        if move_cost.right != MAX && (Option::is_none(&next_cost) || next_cost.unwrap() > pos_score + move_cost.right) {
+            score_card[step.0][step.1] = Some(pos_score + move_cost.right);
+            explore(grid, score_card, step, Cost { up: 1001, down: 1001, left: MAX, right: 1 });
+        }
+    }
+
 }
 
 #[cfg(test)]
@@ -15,9 +119,16 @@ mod tests {
     #[test]
     fn test_part_one() {
         let result = part_one(&advent_of_code::template::read_file("examples", DAY));
-        assert_eq!(result, None);
+        assert_eq!(result, Some(7036));
     }
 
+    #[test]
+    fn test_part_one_2() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(11048));
+    }
+
+    #[ignore]
     #[test]
     fn test_part_two() {
         let result = part_two(&advent_of_code::template::read_file("examples", DAY));