Day 6, Parts 1 + 2!

2022/aoc2022/src/day6.rs

@@ -0,0 +1,52 @@
+use std::collections::HashSet;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+pub fn main(filename: &str) -> std::io::Result<()> {
+    let file = File::open(filename)?;
+    let reader = BufReader::new(file);
+
+    let file_contents: Vec<char> = reader
+        .lines()
+        .map(|l| {
+            l.expect("Couldn't read line")
+                .chars()
+                .collect::<Vec<char>>()
+        })
+        .flatten()
+        .collect();
+
+    let (sop_offset, start_of_packet_marker) = file_contents
+        .windows(4)
+        .enumerate()
+        .find(|(_, w)| HashSet::<&char>::from_iter(w.iter()).len() == 4)
+        .expect("Couldn't find start-of-packet marker");
+
+    let (sow_offset, start_of_window_marker) = file_contents
+        .windows(14)
+        .enumerate()
+        .find(|(_, w)| HashSet::<&char>::from_iter(w.iter()).len() == 14)
+        .expect("Couldn't find start-of-message marker");
+
+    println!(
+        "Part 1: Start-of-packet message is ‘{}’ at offset {}",
+        start_of_packet_marker
+            .into_iter()
+            .map(|c| c.to_string())
+            .collect::<Vec<String>>()
+            .join(""),
+        sop_offset + 4
+    );
+
+    println!(
+        "Part 2: Start-of-packet message is ‘{}’ at offset {}",
+        start_of_window_marker
+            .into_iter()
+            .map(|c| c.to_string())
+            .collect::<Vec<String>>()
+            .join(""),
+        sow_offset + 14
+    );
+
+    Ok(())
+}