1 files changed, 75 insertions, 0 deletions
diff --git a/2021/src/bin/day_1.rs b/2021/src/bin/day_1.rs
new file mode 100644
index 0000000..62ab045
--- /dev/null
+++ b/2021/src/bin/day_1.rs
@@ -0,0 +1,75 @@
+use nom::{
+    character::complete::{line_ending, u64 as nom_u64},
+    combinator::map,
+    multi::separated_list1,
+    IResult,
+};
+use std::fs;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let input = fs::read_to_string("inputs/day_1.txt")?;
+    let sonar_scan = parse_sonar_scan(&input).unwrap().1;
+
+    let simple_increase_counter = count_increases(sonar_scan.iter());
+    dbg!(simple_increase_counter);
+
+    let windowed_sonar_scan = sonar_scan
+        .iter()
+        .zip(sonar_scan.iter().skip(1))
+        .zip(sonar_scan.iter().skip(2))
+        .map(|((depth1, depth2), depth3)| ThreeDepthWindowSum::new([*depth1, *depth2, *depth3]))
+        .collect::<Vec<_>>();
+
+    let windowed_increase_counter = count_increases(windowed_sonar_scan.iter());
+    dbg!(windowed_increase_counter);
+
+    Ok(())
+}
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
+struct Depth(u64);
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
+struct ThreeDepthWindowSum(u64);
+
+impl ThreeDepthWindowSum {
+    fn new(depths: [Depth; 3]) -> ThreeDepthWindowSum {
+        ThreeDepthWindowSum(depths.into_iter().map(|d| d.0).sum())
+    }
+}
+
+fn parse_sonar_scan(input: &str) -> IResult<&str, Vec<Depth>> {
+    separated_list1(line_ending, parse_depth)(input)
+}
+
+fn parse_depth(input: &str) -> IResult<&str, Depth> {
+    map(nom_u64, Depth)(input)
+}
+
+#[derive(Default, Debug)]
+struct DepthIncreaseCounter(u64);
+
+impl DepthIncreaseCounter {
+    fn increment(&mut self) {
+        self.0 += 1;
+    }
+}
+
+fn count_increases<T: Ord>(i: impl IntoIterator<Item = T> + Clone) -> DepthIncreaseCounter {
+    let mut increases = DepthIncreaseCounter::default();
+    for (depth, next_depth) in i.clone().into_iter().zip(i.into_iter().skip(1)) {
+        if next_depth > depth {
+            increases.increment();
+        }
+    }
+    increases
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn parses_a_depth() {
+        assert_eq!(parse_depth("96\n"), Ok(("\n", Depth(96))));
+    }
+}