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Why have many hash map when few do trick

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Bert Peters
2023-12-15 08:54:02 +01:00
parent f898ffd216
commit 6657519179
1 changed files with 12 additions and 10 deletions
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22
2023/src/day15.rs
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@@ -60,26 +60,28 @@ fn parse_commands(i: &[u8]) -> IResult<&[u8], Vec<Command>> {
pub fn part2(input: &[u8]) -> anyhow::Result<String> { pub fn part2(input: &[u8]) -> anyhow::Result<String> {
let commands = parse_input(trim(input), parse_commands)?; let commands = parse_input(trim(input), parse_commands)?;
let mut boxes = [(); 256].map(|_| LinkedHashMap::new()); let mut state = LinkedHashMap::new();
for command in &commands { for command in commands {
match command { match command {
Command::Add(identifier, focal_len) => { Command::Add(identifier, focal_len) => {
*boxes[hash(identifier) as usize] *state.entry(identifier).or_default() = focal_len;
.entry(*identifier)
.or_default() = *focal_len;
} }
Command::Remove(identifier) => { Command::Remove(identifier) => {
boxes[hash(identifier) as usize].remove(identifier); state.remove(identifier);
} }
} }
} }
let mut box_slot = [1; 256];
let mut total = 0; let mut total = 0;
for (i, b) in boxes.iter().enumerate() {
for (slot, &focal_len) in b.values().enumerate() { for (&identifier, &focal_len) in &state {
total += (i as u32 + 1) * (slot as u32 + 1) * focal_len; let index = hash(identifier);
} let box_no = u32::from(index) + 1;
let slot_no = &mut box_slot[index as usize];
total += box_no * *slot_no * focal_len;
*slot_no += 1;
} }
Ok(total.to_string()) Ok(total.to_string())