solution: day 6

src/days.rs

@@ -3,7 +3,7 @@ pub mod d2;
 pub mod d3;
 pub mod d4;
 pub mod d5;
-// pub mod d6;
+pub mod d6;
 // pub mod d7;
 // pub mod d8;
 // pub mod d9;

src/days/d6.rs

@@ -0,0 +1,55 @@
+use crate::prelude::*;
+
+pub type I = Vec<&'static str>;
+pub type O = String;
+
+fn _parse (data: &'static str) -> I {
+    data.lines().collect()
+}
+
+fn _solve (data: &I) -> Vec<M<char, usize>> {
+    let mut m: Vec<M<char, usize>> = vec![M::new(); data[0].len()];
+
+    for line in data {
+        for (col, c) in line.chars().enumerate() {
+            *m[col].entry(c).or_default() += 1;
+        }
+    }
+
+    m
+}
+
+fn _silver (data: &I) -> O {
+    _solve(data).into_iter().map(|v| v.into_iter().max_by_key(|&(_, v)| v).unwrap().0).collect::<String>()
+}
+
+fn _gold (data: &I) -> O {
+    _solve(data).into_iter().map(|v| v.into_iter().min_by_key(|&(_, v)| v).unwrap().0).collect::<String>()
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    fn read () -> I {
+        let data = inc!(6);
+        _parse(data)
+    }
+
+
+    #[test]
+    fn silver () {
+        let data = read();
+        let ans = _silver(&data);
+
+        assert_eq!(ans, s!("gebzfnbt"))
+    }
+
+    #[test]
+    fn gold () {
+        let data = read();
+        let ans = _gold(&data);
+
+        assert_eq!(ans, s!("fykjtwyn"))
+    }
+}