day 09

2023/day-09/src/bin/part1.rs

@@ -0,0 +1,9 @@
+use color_eyre::Result;
+use day_09::part1::process;
+
+fn main() -> Result<()> {
+    let file = include_str!("../../input1.txt");
+    let result = process(file)?;
+    println!("{}", result);
+    Ok(())
+}

2023/day-09/src/bin/part2.rs

@@ -0,0 +1,9 @@
+use color_eyre::Result;
+use day_09::part2::process;
+
+fn main() -> Result<()> {
+    let file = include_str!("../../input2.txt");
+    let result = process(file)?;
+    println!("{}", result);
+    Ok(())
+}

2023/day-09/src/lib.rs

@@ -0,0 +1,2 @@
+pub mod part1;
+pub mod part2;

2023/day-09/src/part1.rs

@@ -0,0 +1,46 @@
+use color_eyre::Result;
+
+use itertools::{Itertools, Position};
+
+fn process_line(line: &str) -> i64 {
+    let mut nums = line
+        .split_whitespace()
+        .map(|num| num.parse::<i64>().unwrap())
+        .collect::<Vec<_>>();
+
+    let mut end_nums = Vec::new();
+
+    while !nums.iter().all(|num| num == &0) {
+        nums = nums
+            .iter()
+            .tuple_windows()
+            .with_position()
+            .map(|(pos, (left, right))| {
+                if let Position::Last | Position::Only = pos {
+                    end_nums.push(*right)
+                }
+                right - left
+            })
+            .collect()
+    }
+    end_nums.iter().sum()
+}
+
+pub fn process(input: &str) -> Result<i64> {
+    let total = input.lines().map(process_line).sum();
+    Ok(total)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_process() -> Result<()> {
+        let input = "0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45";
+        assert_eq!(114, process(input)?);
+        Ok(())
+    }
+}

2023/day-09/src/part2.rs

@@ -0,0 +1,48 @@
+use color_eyre::Result;
+
+use itertools::{Itertools, Position};
+
+fn process_line(line: &str) -> i64 {
+    let mut nums = line
+        .split_whitespace()
+        .map(|num| num.parse::<i64>().unwrap())
+        .collect::<Vec<_>>();
+
+    let mut start_nums = Vec::new();
+
+    while !nums.iter().all(|num| num == &0) {
+        nums = nums
+            .iter()
+            .tuple_windows()
+            .with_position()
+            .map(|(pos, (left, right))| {
+                if let Position::First | Position::Only = pos {
+                    start_nums.push(*left)
+                }
+                right - left
+            })
+            .collect()
+    }
+    dbg!(&start_nums);
+    let result = start_nums.iter().rev().fold(0, |acc, num| num - acc);
+    result
+}
+
+pub fn process(input: &str) -> Result<i64> {
+    let total = input.lines().map(process_line).sum();
+    Ok(total)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_process() -> Result<()> {
+        let input = "0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45";
+        assert_eq!(2, process(input)?);
+        Ok(())
+    }
+}