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advent-of-code-2022/day6/src/main.rs
2022-12-06 13:54:34 -05:00

51 lines
1.5 KiB
Rust

fn find_num_chars_before_marker(chars: &Vec<char>, marker_size: usize) -> usize {
let mut iter = chars.iter().enumerate();
'outer: for (i, _) in &mut iter {
// Look marker_size -1 characters forward so we can check for duplicate characters
let mut cursor: Vec<char> = Vec::new();
for n in 0..marker_size {
cursor.push(*chars.get(i + n).unwrap());
}
cursor.sort_unstable();
// If there's a duplicate character, go forward
for (n, ch) in cursor.iter().enumerate() {
if let Some(other) = cursor.get(n + 1) {
if ch == other {
continue 'outer;
}
}
}
// Since we are looking farther than the current iteration,
// we need to add the marker size that to the returned index
return i + marker_size;
}
panic!("Marker not found");
}
fn find_packet_marker(chars: &Vec<char>) -> usize {
find_num_chars_before_marker(chars, 4)
}
fn find_message_marker(chars: &Vec<char>) -> usize {
find_num_chars_before_marker(chars, 14)
}
fn main() {
let file_str = include_str!("input.txt");
let chars: Vec<char> = file_str.chars().collect();
println!(
"Part 1: Number of characters before start-of-packet marker: {}",
find_packet_marker(&chars)
);
println!(
"Part 2: Number of characters before start-of-message marker: {}",
find_message_marker(&chars)
);
}