2020: day06: part 1

aoc2020/src/day06.rs

@@ -0,0 +1,71 @@
+use std::collections::HashSet;
+use std::fmt::Write;
+
+const INPUT: &str = include_str!("../input/day06.txt");
+
+pub fn run() -> aoc::Result<String> {
+    let mut res = String::with_capacity(128);
+
+    writeln!(res, "part 1: {}", part1(INPUT)?)?;
+
+    Ok(res)
+}
+
+fn get_groups(input: &str) -> aoc::Result<Vec<Group>> {
+    let mut groups = Vec::new();
+
+    let mut answers = Vec::new();
+
+    for line in input.lines() {
+        if line.is_empty() {
+            groups.push(Group {
+                answers: answers.clone(),
+            });
+            answers.clear();
+        } else {
+            let person_answers = line.bytes().collect();
+            answers.push(person_answers);
+        }
+    }
+
+    if !answers.is_empty() {
+        groups.push(Group { answers });
+    }
+
+    Ok(groups)
+}
+
+fn part1(input: &str) -> aoc::Result<usize> {
+    let groups = get_groups(input)?;
+
+    Ok(groups
+        .iter()
+        .map(|group| {
+            group.answers.iter().fold(HashSet::new(), |set, answers| {
+                set.union(answers).copied().collect()
+            })
+        })
+        .map(|set| set.len())
+        .sum())
+}
+
+struct Group {
+    answers: Vec<HashSet<u8>>,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static PROVIDED: &'static str = include_str!("../input/day06_provided.txt");
+
+    #[test]
+    fn part1_provided() {
+        assert_eq!(part1(PROVIDED).unwrap(), 11);
+    }
+
+    #[test]
+    fn part1_real() {
+        assert_eq!(part1(INPUT).unwrap(), 6382);
+    }
+}

aoc2020/src/lib.rs

@@ -3,3 +3,4 @@ pub mod day02;
 pub mod day03;
 pub mod day04;
 pub mod day05;
+pub mod day06;

aoc2020/src/main.rs

@@ -6,9 +6,17 @@ use aoc2020::day02;
 use aoc2020::day03;
 use aoc2020::day04;
 use aoc2020::day05;
+use aoc2020::day06;
 
 fn main() -> Result<()> {
-    let days: &[DayFunc] = &[day01::run, day02::run, day03::run, day04::run, day05::run];
+    let days: &[DayFunc] = &[
+        day01::run,
+        day02::run,
+        day03::run,
+        day04::run,
+        day05::run,
+        day06::run,
+    ];
 
     aoc::run(days)
 }