1 files changed, 63 insertions, 0 deletions
diff --git a/d06/src/main.rs b/d06/src/main.rs
new file mode 100644
index 0000000..e482735
--- /dev/null
+++ b/d06/src/main.rs
@@ -0,0 +1,63 @@
+use std::collections::HashMap;
+use std::fs;
+
+fn solve_puzzle(lines: &Vec<&str>, use_max: bool) -> String {
+    let mut freqs = Vec::new();
+    for _i in 0..lines[0].len() {
+        let hm: HashMap<char, usize> = HashMap::new();
+        freqs.push(hm);
+    }
+
+    // Count char occurrences at each index in line
+    for line in lines {
+        for (i, c) in line.chars().enumerate() {
+            *freqs[i].entry(c).or_insert(0) += 1;
+        }
+    }
+
+    let mut result = String::new();
+    for hm in freqs {
+        let c = if use_max {
+            // Part 1: take most common character
+            hm.into_iter().max_by_key(|x| x.1).unwrap().0
+        } else {
+            // Part 2: take least common character
+            hm.into_iter().min_by_key(|x| x.1).unwrap().0
+        };
+        result.push(c);
+    }
+
+    result
+}
+
+fn main() {
+    // Read messages from input text file
+    let input = fs::read_to_string("input.txt").unwrap();
+    let lines = input.lines().collect();
+
+    // Part 1 gives "mlncjgdg" for me
+    println!("Part 1 solution: {}", solve_puzzle(&lines, true));
+
+    // Part 2 gives "bipjaytb" for me
+    println!("Part 2 solution: {}", solve_puzzle(&lines, false));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EXAMPLE1_LINES: [&str; 16] = [
+        "eedadn", "drvtee", "eandsr", "raavrd", "atevrs", "tsrnev", "sdttsa", "rasrtv",
+        "nssdts", "ntnada", "svetve", "tesnvt", "vntsnd", "vrdear", "dvrsen", "enarar",
+    ];
+
+    #[test]
+    fn part1_example1() {
+        assert_eq!(solve_puzzle(&Vec::from(EXAMPLE1_LINES), true), "easter");
+    }
+
+    #[test]
+    fn part2_example1() {
+        assert_eq!(solve_puzzle(&Vec::from(EXAMPLE1_LINES), false), "advent");
+    }
+}