day6

Cargo.toml

@@ -31,3 +31,7 @@ path = "src/day04/main.rs"
 [[bin]]
 name = "day05"
 path = "src/day05/main.rs"
+
+[[bin]]
+name = "day06"
+path = "src/day06/main.rs"

src/day06/main.rs

@@ -0,0 +1,98 @@
+use anyhow::Result;
+use std::collections::HashSet;
+use thiserror::Error;
+
+static INPUT: &str = include_str!("../../input06");
+
+fn main() -> Result<()> {
+    let uniq_votes: usize = GroupParser::from(INPUT)
+        .into_iter()
+        .map(|group| group.uniq_votes)
+        .sum();
+    println!("uniqe votes: {}", uniq_votes);
+    let approval_votes: usize = GroupParser::from(INPUT)
+        .into_iter()
+        .map(|group| group.approval_votes)
+        .sum();
+    println!("approval votes: {}", approval_votes);
+    Ok(())
+}
+
+struct GroupParser<'a> {
+    inner: &'a str,
+}
+
+impl<'a> From<&'a str> for GroupParser<'a> {
+    fn from(data: &'a str) -> Self {
+        GroupParser { inner: data }
+    }
+}
+
+impl<'a> Iterator for GroupParser<'a> {
+    type Item = Group;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        while self.inner.len() > 0 {
+            let mut splitted = self.inner.splitn(2, "\n\n");
+            let line = splitted.next().unwrap();
+            self.inner = splitted.next().or(Some(""))?;
+
+            match line {
+                "" => (),
+                line => return Some(Group::from(line)),
+            }
+        }
+        None
+    }
+}
+
+struct Group {
+    uniq_votes: usize,
+    approval_votes: usize,
+}
+
+impl From<&str> for Group {
+    fn from(value: &str) -> Self {
+        let uniq_votes: HashSet<char> = value.chars().filter(|&c| c.is_alphabetic()).collect();
+
+        let approval_votes: HashSet<char> = value
+            .trim()
+            .lines()
+            .map(|line| {
+                line.chars().filter(|&c| c.is_alphabetic()).collect()
+            })
+            .fold(
+                "abcdefghijklmnopqrstuvwxyz".chars().collect(),
+                |set, chars| set.intersection(&chars).cloned().collect(),
+            );
+
+        Group {
+            uniq_votes: uniq_votes.len(),
+            approval_votes: approval_votes.len(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn fails() {
+        let uniq_votes: usize = GroupParser::from(INPUT)
+            .into_iter()
+            .map(|group| group.uniq_votes)
+            .sum();
+        assert_ne!(uniq_votes, 46);
+        assert_ne!(uniq_votes, 15008);
+    }
+
+    #[test]
+    fn day1() {
+        let uniq_votes: usize = GroupParser::from(INPUT)
+            .into_iter()
+            .map(|group| group.uniq_votes)
+            .sum();
+        assert_eq!(uniq_votes, 6587);
+    }
+}