puzzle 2-1

1 files changed, 64 insertions, 0 deletions

diff --git a/src/2020/2/mod.rs b/src/2020/2/mod.rs
new file mode 100644
index 0000000..88d3f5b
--- /dev/null
+++ b/src/2020/2/mod.rs
@@ -0,0 +1,64 @@
+use anyhow::Context as _;
+use std::io::BufRead as _;
+
+struct Line {
+    c: char,
+    min_times: usize,
+    max_times: usize,
+    password: String,
+}
+
+impl Line {
+    fn parse(line: &str) -> anyhow::Result<Self> {
+        let rx = regex::Regex::new(r"^([0-9]+)-([0-9]+) (.): (.*)$").unwrap();
+        let captures =
+            rx.captures(line).context("line failed to match regex")?;
+        let c = captures
+            .get(3)
+            .unwrap()
+            .as_str()
+            .parse()
+            .context("invalid policy char")?;
+        let min_times = captures
+            .get(1)
+            .unwrap()
+            .as_str()
+            .parse()
+            .context("invalid policy lower bound")?;
+        let max_times = captures
+            .get(2)
+            .unwrap()
+            .as_str()
+            .parse()
+            .context("invalid policy upper bound")?;
+        let password = captures.get(4).unwrap().as_str().to_string();
+        Ok(Self {
+            c,
+            min_times,
+            max_times,
+            password,
+        })
+    }
+
+    fn valid(&self) -> bool {
+        let count = self.password.chars().filter(|c| *c == self.c).count();
+        count >= self.min_times && count <= self.max_times
+    }
+}
+
+pub fn part1() -> anyhow::Result<()> {
+    let f = std::fs::File::open("data/2.txt")
+        .context("couldn't find data file 2.txt")?;
+    let f = std::io::BufReader::new(f);
+    let lines = f
+        .lines()
+        .map(|l| Line::parse(&l.context("failed to read a line")?))
+        .collect::<anyhow::Result<Vec<Line>>>()?;
+    let count = lines.iter().filter(|l| l.valid()).count();
+    println!("{}", count);
+    Ok(())
+}
+
+pub fn part2() -> anyhow::Result<()> {
+    todo!()
+}