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use std::collections::VecDeque;
static DAY: u8 = 9;
fn main() {
let input = advent::read_file(DAY);
println!("{DAY}a: {}", fs_checksum(&input));
println!("{DAY}b: {}", 0);
}
fn fs_checksum(map: &str) -> usize {
let counts = map.trim_end().chars().map(|x| x.to_digit(10).unwrap() as u8).collect::<Vec<_>>();
let mut file_ids = VecDeque::new();
let mut block_sizes = VecDeque::new();
let mut holes = VecDeque::new();
for (id, c) in counts.chunks(2).enumerate() {
let file = c[0];
for _ in 0 .. file {
file_ids.push_back(id);
}
block_sizes.push_back(file);
if c.len() == 2 {
let free = c[1];
holes.push_back(free);
}
}
let mut disk = Vec::new();
disk.reserve(map.len() * 10);
while !holes.is_empty() && !file_ids.is_empty() {
let blocks_front = block_sizes.pop_front().unwrap() as usize;
for _ in 0 .. blocks_front.min(file_ids.len()) {
let front = file_ids.pop_front().unwrap();
disk.push(front);
}
let holes_front = holes.pop_front().unwrap() as usize;
for _ in 0 .. holes_front.min(file_ids.len()) {
let back = file_ids.pop_back().unwrap();
disk.push(back);
}
}
disk.iter()
.enumerate()
.map(|(i, block)| i * block)
.sum()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = "2333133121414131402";
assert_eq!(fs_checksum(input), 1928);
}
}
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