day9

aoc_2024/src/day8.rs

@@ -1,7 +1,6 @@
 use hashbrown::{HashMap, HashSet};
 
 use aoc_runner_derive::{aoc, aoc_generator};
-use num::integer::gcd;
 
 type Input = ((isize, isize), Vec<Vec<(isize, isize)>>);
 
@@ -94,6 +93,7 @@ mod tests {
             )),
             14
         );
+        assert_eq!(part1(&parse(include_str!("../input/2024/day8.txt"))), 273);
     }
 
     #[test]
@@ -104,7 +104,6 @@ mod tests {
             )),
             34
         );
-
         assert_eq!(part2(&parse(include_str!("../input/2024/day8.txt"))), 1017);
     }
 }

aoc_2024/src/day9.rs

@@ -0,0 +1,106 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+type Input = Vec<usize>;
+
+#[aoc_generator(day9)]
+fn parse(input: &str) -> Input {
+    input
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as usize)
+        .collect()
+}
+
+#[aoc(day9, part1)]
+fn part1(input: &Input) -> usize {
+    let mut sum = 0;
+    let mut len = input.chunks(2).map(|c| c[0]).sum::<usize>();
+    let mut l_idx = 0;
+    let mut l_pos = 0;
+    let mut r_idx = input.len() + 1;
+    let mut r_left = 0;
+    while len > 0 {
+        if l_idx % 2 == 0 {
+            for _ in 0..input[l_idx] {
+                // println!("l {}*{}", l_pos, l_idx / 2);
+                // print!("{}", l_idx / 2);
+                len -= 1;
+                sum += (l_idx / 2) * l_pos;
+                l_pos += 1;
+                if len == 0 {
+                    break;
+                }
+            }
+            l_idx += 1;
+        } else {
+            for _ in 0..input[l_idx] {
+                while r_left == 0 {
+                    r_idx -= 2;
+                    r_left = input[r_idx];
+                }
+                // println!("r {}*{}", l_pos, r_idx / 2);
+                // print!("{}", r_idx / 2);
+                len -= 1;
+                sum += (r_idx / 2) * l_pos;
+                l_pos += 1;
+                r_left -= 1;
+                if len == 0 {
+                    break;
+                }
+            }
+            l_idx += 1;
+        }
+    }
+    sum
+}
+
+#[aoc(day9, part2)]
+fn part2(input: &Input) -> usize {
+    let mut input = input
+        .iter()
+        .map(|c| (0, *c, *c))
+        .collect::<Vec<(usize, usize, usize)>>();
+    for i in 1..input.len() {
+        input[i].0 = input[i - 1].0 + input[i - 1].1;
+    }
+    // println!("{:?}", &input);
+    let mut sum = 0;
+    for r_idx in (0..input.len()).step_by(2).rev() {
+        let val = r_idx / 2;
+        let count = input[r_idx].2;
+        // println!("attempt: {:?}", input[r_idx]);
+        for l_idx in (1..r_idx).step_by(2) {
+            if input[l_idx].1 >= input[r_idx].2 {
+                // print!("{:?}", input[l_idx]);
+                input[r_idx].0 = input[l_idx].0;
+                input[l_idx].1 -= input[r_idx].2;
+                input[l_idx].0 += input[r_idx].2;
+                input[l_idx - 1].1 += input[r_idx].2;
+                // println!(" -> {:?}", input[l_idx]);
+                break;
+            }
+        }
+        for i in 0..count {
+            // println!("{}*{}", (input[r_idx].0 + i), val);
+            sum += val * (input[r_idx].0 + i);
+            // input[r_idx].0 += 1;
+        }
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&parse("2333133121414131402")), 1928);
+        // assert_eq!(part1(&parse(include_str!("../input/2024/day8.txt"))), 273);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&parse("2333133121414131402")), 2858);
+        // assert_eq!(part2(&parse(include_str!("../input/2024/day8.txt"))), 1017);
+    }
+}

aoc_2024/src/lib.rs

@@ -1,4 +1,3 @@
-mod day8;
 mod day1;
 mod day2;
 mod day3;
@@ -6,6 +5,8 @@ mod day4;
 mod day5;
 mod day6;
 mod day7;
+mod day8;
+mod day9;
 
 extern crate aoc_runner;