Move to 2016 directory

1 files changed, 87 insertions, 0 deletions

diff --git a/2016/src/bin/day06.rs b/2016/src/bin/day06.rs
new file mode 100644
index 0000000..7f8a516
--- /dev/null
+++ b/2016/src/bin/day06.rs
@@ -0,0 +1,87 @@
+use std::collections::HashMap;
+use std::io::{self, Read};
+
+fn frequencies(chars: &[char]) -> HashMap<char, u32> {
+    let mut map = HashMap::new();
+    for &ch in chars {
+        *map.entry(ch).or_insert(0) += 1;
+    }
+    map
+}
+
+fn solve1(input: &str) -> String {
+    let len = input.find('\n').unwrap_or(input.len());
+    let mut columns = vec![Vec::new(); len];
+
+    for line in input.lines() {
+        for (i, ch) in line.chars().enumerate() {
+            columns[i].push(ch);
+        }
+    }
+
+    columns.into_iter()
+        .map(|column| frequencies(&column))
+        .map(IntoIterator::into_iter)
+        .map(|iter| iter.max_by_key(|&(_, v)| v))
+        .map(Option::unwrap)
+        .map(|(ch, _)| ch)
+        .collect()
+}
+
+fn solve2(input: &str) -> String {
+    let len = input.find('\n').unwrap_or(input.len());
+    let mut columns = vec![Vec::new(); len];
+
+    for line in input.lines() {
+        for (i, ch) in line.chars().enumerate() {
+            columns[i].push(ch);
+        }
+    }
+
+    columns.into_iter()
+        .map(|column| frequencies(&column))
+        .map(IntoIterator::into_iter)
+        .map(|iter| iter.min_by_key(|&(_, v)| v))
+        .map(Option::unwrap)
+        .map(|(ch, _)| ch)
+        .collect()
+}
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_to_string(&mut input).unwrap();
+
+    println!("Part 1: {}", solve1(&input));
+    println!("Part 2: {}", solve2(&input));
+}
+
+#[cfg(test)]
+const TEST_INPUT: &'static str = "
+eedadn
+drvtee
+eandsr
+raavrd
+atevrs
+tsrnev
+sdttsa
+rasrtv
+nssdts
+ntnada
+svetve
+tesnvt
+vntsnd
+vrdear
+dvrsen
+enarar
+";
+
+
+#[test]
+fn part1() {
+    assert_eq!("easter", solve1(TEST_INPUT.trim()));
+}
+
+#[test]
+fn part2() {
+    assert_eq!("advent", solve2(TEST_INPUT.trim()));
+}