Day 6 speed update

day6/src/main.rs

@@ -1,22 +1,29 @@
 use std::{collections::HashSet, fs::read_to_string};
 
-fn find_nonrecuring_sequence(input: &[char], length: usize) -> usize {
+fn find_nonrecuring_sequence(input: &[char], length: usize) -> Option<usize> {
     input
         .windows(length)
         .enumerate()
-        .find(|(_, chars)| chars.iter().collect::<HashSet<_>>().len() == length)
-        .unwrap_or((input.len(), &[]))
-        .0
-        + length
+        .find(|(_, chars)| {
+            for i in 1..chars.len() {
+                if chars[..i].contains(&chars[i]) {
+                    return false;
+                }
+            }
+            true
+        })
+        //.find(|(_, chars)| chars.iter().collect::<HashSet<_>>().len() == length)
+        .map(|(i, _)| i + length)
 }
 
-fn main() {
+fn main() -> Result<(), std::io::Error> {
     const PACKET_START_LENGTH: usize = 4;
     const MESSAGE_START_LENGTH: usize = 14;
-    let input = read_to_string("input.txt").unwrap();
+    let input = read_to_string("input.txt")?;
     let input = input.chars().collect::<Vec<_>>();
     let packet_marker = find_nonrecuring_sequence(&input, PACKET_START_LENGTH);
-    println!("first packet marker at {packet_marker}");
+    println!("first packet marker at {packet_marker:?}");
     let message_marker = find_nonrecuring_sequence(&input, MESSAGE_START_LENGTH);
-    println!("first message marker at {message_marker}");
+    println!("first message marker at {message_marker:?}");
+    Ok(())
 }