Day 10 part 2

2024/rust/src/day10.rs

@@ -17,7 +17,7 @@ fn part1(input: &str) -> usize {
         for (x, height) in row.iter().enumerate() {
             let mut scores = HashSet::new();
             if *height == 0 {
-                find_paths_to_nines(&map, *height, x, y, &mut scores);
+                capture_scores(&map, *height, x, y, &mut scores);
                 sum += scores.len();
             }
             println!("{x} {y} {height}");
@@ -26,7 +26,7 @@ fn part1(input: &str) -> usize {
     sum
 }
 
-fn find_paths_to_nines(
+fn capture_scores(
     map: &Vec<Vec<u8>>,
     height: u8,
     x: usize,
@@ -49,13 +49,50 @@ fn find_paths_to_nines(
         let next_height = map[ny][nx];
         if next_height.saturating_sub(height) == 1 {
             println!("{height} -> {next_height} at {nx},{ny}");
-            find_paths_to_nines(map, next_height, nx, ny, scores)
+            capture_scores(map, next_height, nx, ny, scores)
         }
     }
 }
 
 fn part2(input: &str) -> usize {
-    0
+    println!("{input}");
+    let mut sum = 0;
+    let map: Vec<Vec<u8>> = input
+        .lines()
+        .map(|l| l.bytes().map(|b| b - b'0').collect())
+        .collect();
+    for (y, row) in map.iter().enumerate() {
+        for (x, height) in row.iter().enumerate() {
+            if *height == 0 {
+                sum += find_paths_to_nines(&map, *height, x, y);
+            }
+            println!("{x} {y} {height}");
+        }
+    }
+    sum
+}
+
+fn find_paths_to_nines(map: &Vec<Vec<u8>>, height: u8, x: usize, y: usize) -> usize {
+    let mut sum = 0;
+    if height == 9 {
+        return 1;
+    }
+    for (nx, ny) in [
+        (x + 1, y),
+        (x.saturating_sub(1), y),
+        (x, y + 1),
+        (x, y.saturating_sub(1)),
+    ] {
+        if nx >= map[0].len() || ny >= map.len() {
+            continue;
+        }
+        let next_height = map[ny][nx];
+        if next_height.saturating_sub(height) == 1 {
+            println!("{height} -> {next_height} at {nx},{ny}");
+            sum += find_paths_to_nines(map, next_height, nx, ny)
+        }
+    }
+    sum
 }
 
 #[cfg(test)]
@@ -73,6 +110,6 @@ mod tests {
 01329801
 10456732"#;
         assert_eq!(part1(input), 36);
-        assert_eq!(part2(input), 0);
+        assert_eq!(part2(input), 81);
     }
 }