day09: Initial solution

README.md

@@ -16,6 +16,8 @@
   - [solution](src/day07.rs)
 - [Day 8: Haunted Wasteland](https://adventofcode.com/2023/day/8)
   - [solution](src/day08.rs)
+- [Day 9: Mirage Maintenance](https://adventofcode.com/2023/day/9)
+  - [solution](src/day09.rs)
 <!-- Insert before -->
 
 See:

justfile

@@ -1,3 +1,3 @@
 commit-input:
-    cd input && git add . && git commit -m "$(git status --porcelain | sed 's/A /Add/')" && git push
+    cd input && [[ -n $(git status -s) ]] && git add . && git commit -m "$(git status --porcelain | sed 's/A /Add/')" && git push
 

src/day09.rs

@@ -0,0 +1,114 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+use crate::common::utils::parse_split;
+
+#[aoc_generator(day9)]
+pub fn generator(input: &str) -> Vec<Vec<i64>> {
+    input.lines().map(|line| parse_split(line, ' ')).collect()
+}
+
+fn diff(v: &[i64]) -> Vec<i64> {
+    v.windows(2).map(|x| x[1] - x[0]).collect()
+}
+
+fn process(v: &[i64]) -> i64 {
+    let mut v = v.to_vec();
+    let mut differences = vec![v.to_vec()];
+
+    loop {
+        let v2 = diff(&v);
+        let all_zeros = v2.iter().all(|&x| x == 0);
+        if all_zeros {
+            break;
+        }
+
+        differences.push(v2.clone());
+
+        v = v2;
+    }
+
+    let mut constant = 0;
+    while let Some(d) = differences.pop() {
+        let last = d.last().copied().unwrap() + constant;
+        constant = last;
+    }
+
+    constant
+}
+
+fn process2(v: &[i64]) -> i64 {
+    let mut v = v.to_vec();
+    let mut differences = vec![v.to_vec()];
+
+    loop {
+        let v2 = diff(&v);
+        let all_zeros = v2.iter().all(|&x| x == 0);
+        if all_zeros {
+            break;
+        }
+
+        differences.push(v2.clone());
+
+        v = v2;
+    }
+
+    let mut constant = 0;
+    while let Some(d) = differences.pop() {
+        let last = d.first().copied().unwrap() - constant;
+        constant = last;
+    }
+
+    constant
+}
+
+#[aoc(day9, part1)]
+pub fn part1(inputs: &[Vec<i64>]) -> i64 {
+    inputs.iter().map(|x| process(x)).sum()
+}
+
+#[aoc(day9, part2)]
+pub fn part2(inputs: &[Vec<i64>]) -> i64 {
+    inputs.iter().map(|x| process2(x)).sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &str = r"0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45";
+
+    #[test]
+    pub fn input_test() {
+        println!("{:?}", generator(SAMPLE));
+
+        // assert_eq!(generator(SAMPLE), Object());
+    }
+
+    #[test]
+    pub fn part1_test() {
+        assert_eq!(part1(&generator(SAMPLE)), 114);
+    }
+
+    #[test]
+    pub fn part2_test() {
+        assert_eq!(part2(&generator(SAMPLE)), 2);
+    }
+
+    mod regression {
+        use super::*;
+
+        const INPUT: &str = include_str!("../input/2023/day9.txt");
+        const ANSWERS: (i64, i64) = (1834108701, 993);
+
+        #[test]
+        pub fn test() {
+            let input = INPUT.trim_end_matches('\n');
+            let output = generator(input);
+
+            assert_eq!(part1(&output), ANSWERS.0);
+            assert_eq!(part2(&output), ANSWERS.1);
+        }
+    }
+}

src/lib.rs

@@ -9,5 +9,6 @@ pub mod day05;
 pub mod day06;
 pub mod day07;
 pub mod day08;
+pub mod day09;
 // Insert before
 aoc_lib! { year = 2023 }