Solve day 9

input/09-0.in

@@ -0,0 +1 @@
+2333133121414131402

src/bin/09.rs

@@ -0,0 +1,91 @@
+use itertools::Itertools;
+
+fn main() {
+    let text = std::fs::read_to_string("input/09-1.in").unwrap();
+
+    let mut map = text
+        .trim()
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as usize)
+        .collect::<Vec<_>>();
+
+    dbg!(map.len());
+
+    let mut sum = 0;
+    let mut i = 0;
+    let mut pos = 0;
+    while i < map.len() {
+        sum += (0..map[i]).map(|c| (c + pos) * i / 2).sum::<usize>();
+
+        pos += map[i];
+
+        // println!("{pos} {sum}");
+        while i < (map.len() - 1) && map[i + 1] > 0 {
+            while map[map.len() - 1] == 0 {
+                map.pop();
+                map.pop();
+            }
+
+            let l = map.len() - 1;
+            if i < l {
+                map[l] -= 1;
+
+                sum += (l / 2) * pos;
+                // println!("{i} {pos} {sum} {map:?}");
+                map[i + 1] -= 1;
+            }
+            pos += 1;
+            // println!("{pos} {sum}");
+        }
+
+        i += 2;
+    }
+
+    println!("{}", sum);
+
+    let mut pos = 0;
+    let mut map = text
+        .trim()
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as usize)
+        .map(|d| {
+            let r = (d, pos);
+            pos += d;
+            r
+        })
+        .enumerate()
+        .filter_map(|(i, d)| if i % 2 == 0 { Some(d) } else { None })
+        .enumerate()
+        .map(|(i, (d, pos))| (i, d, pos))
+        .collect::<Vec<_>>();
+
+    // println!("{map:?}");
+
+    let mut i = map.len() - 1;
+    let mut id = i;
+    while id > 0 {
+        while i > 0 && map[i].0 != id {
+            i -= 1;
+        }
+
+        let size = map[i].1;
+        if let Some((l, _)) = map[0..i]
+            .iter()
+            .zip(map[1..].iter())
+            .find_position(|(left, right)| size <= right.2 - (left.1 + left.2))
+        {
+            let (_, len, _) = map.remove(i);
+            map.insert(l + 1, (id, len, map[l].1 + map[l].2))
+        }
+
+        // println!("{map:?}");
+        id -= 1;
+    }
+
+    let t = map
+        .iter()
+        .flat_map(|&(id, c, pos)| (0..c).map(move |i| (pos + i) * id))
+        .sum::<usize>();
+
+    println!("{t}");
+}