1 files changed, 47 insertions, 0 deletions
diff --git a/2022/src/day06.rs b/2022/src/day06.rs
new file mode 100644
index 0000000..8bbfe6d
--- /dev/null
+++ b/2022/src/day06.rs
@@ -0,0 +1,47 @@
+mod utils;
+use utils::read_input;
+
+fn main() {
+    let input = read_input();
+
+    println!("Part 1: {}", find_chunk_nodup::<4>(&input));
+    println!("Part 2: {}", find_chunk_nodup::<14>(&input));
+}
+
+fn find_chunk_nodup<const N: usize>(input: &str) -> usize {
+    let mut window = ['a'; N];
+    let mut chars = input.chars();
+
+    // Fill up initial window
+    for item in window.iter_mut() {
+        *item = chars.next().unwrap();
+    }
+
+    for i in 0..input.len() {
+        // Shuffle everything in window down
+        for j in 0..N - 1 {
+            window[j] = window[j + 1];
+        }
+        window[N - 1] = chars.next().unwrap();
+
+        if window
+            .iter()
+            .fold(Some(0), |acc, chr| add_char(acc?, *chr))
+            .is_some()
+        {
+            return i + N + 1;
+        }
+    }
+
+    panic!("no solution!")
+}
+
+#[inline]
+fn add_char(bits: u32, chr: char) -> Option<u32> {
+    let add = 1 << (chr.to_ascii_lowercase() as u32 - 97);
+    if (bits | add) != bits {
+        Some(bits | add)
+    } else {
+        None
+    }
+}