10th day

Author: majcn

data/examples/10.txt

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+89010123
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src/bin/10.rs

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+advent_of_code::solution!(10);
+
+use advent_of_code::maneatingape::grid::*;
+use advent_of_code::maneatingape::hash::*;
+use advent_of_code::maneatingape::point::*;
+
+fn parse_data(input: &str) -> Grid<u8> {
+    Grid::parse(input)
+}
+
+fn part_x(grid: &Grid<u8>) -> FastMap<(Point, Point), u32> {
+    let mut start_positions = vec![];
+    for y in 0..grid.height {
+        for x in 0..grid.width {
+            if grid[Point::new(x, y)] == b'0' {
+                start_positions.push(Point::new(x, y));
+            }
+        }
+    }
+
+    let mut result = FastMap::new();
+    for start_position in start_positions {
+        let mut paths = vec![(b'0', start_position)];
+
+        while let Some((height, location)) = paths.pop() {
+            if height == b'9' {
+                *result.entry((start_position, location)).or_insert(0) += 1;
+                continue;
+            }
+
+            for step in [LEFT, RIGHT, UP, DOWN] {
+                let next_location = location + step;
+                if grid.contains(next_location) && grid[next_location] == height + 1 {
+                    paths.push((height + 1, next_location));
+                }
+            }
+        }
+    }
+
+    result
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let grid = parse_data(input);
+
+    let result = part_x(&grid).len() as u32;
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let grid = parse_data(input);
+
+    let result = part_x(&grid).values().sum();
+
+    Some(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, Some(36));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(81));
+    }
+}