Added day 9-1

src/days/day9.rs

@@ -0,0 +1,37 @@
+use std::{path::Path, str::FromStr};
+
+use crate::{error::AdventError, input::read_into_vec};
+
+struct Series(Vec<i32>);
+
+impl FromStr for Series {
+    type Err = AdventError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(Series(s.trim().split_whitespace().map(|x| {
+            Ok(i32::from_str(x)?)
+        }).collect::<Result<Vec<i32>, AdventError>>()?))
+    }
+}
+
+pub fn one() -> Result<u64, AdventError> {
+    let series = read_into_vec::<Series>(Path::new("resources/input9.txt"))?;
+    Ok(series.iter().fold(Ok(0i64), | acc: Result<i64, AdventError>, Series(series) | {
+        Ok(acc? + (predict_next(series)? as i64))
+    })? as u64)
+}
+
+fn predict_next(series: &[i32]) -> Result<i32, AdventError> {
+    if !series.iter().all(|x| *x == 0) {
+        let diff_vec: Vec<i32> = series.iter().zip(series.iter().skip(1)).map(|(lh, rh)| {
+            *rh - *lh
+        }).collect::<Vec<i32>>();
+        Ok(series.last().ok_or(AdventError("No last element in array?".into()))? + predict_next(&diff_vec)?)
+    } else {
+        Ok(0)
+    }
+}
+
+pub fn two() -> Result<u64, AdventError> {
+    Ok(0)
+}

src/days/mod.rs

@@ -5,4 +5,5 @@ pub mod day4;
 pub mod day5;
 pub mod day6;
 pub mod day7;
-pub mod day8;
+pub mod day8;
+pub mod day9;

src/main.rs

@@ -19,6 +19,7 @@ fn main() -> Result<(), AdventError> {
         (day6::one as fn() -> Result<u64, AdventError>, day6::two as fn() -> Result<u64, AdventError>),
         (day7::one as fn() -> Result<u64, AdventError>, day7::two as fn() -> Result<u64, AdventError>),
         (day8::one as fn() -> Result<u64, AdventError>, day8::two as fn() -> Result<u64, AdventError>),
+        (day9::one as fn() -> Result<u64, AdventError>, day9::two as fn() -> Result<u64, AdventError>),
     ];
 
     if env::args().len() == 1 {