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day9: use part 2 'inodes' table to speed up part 1

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This commit is contained in:
Keenan Tims 2024-12-08 23:51:51 -08:00
parent 2bc751dd0d
commit b08c8fbd80
Signed by: ktims
GPG Key ID: 11230674D69038D4
1 changed files with 7 additions and 28 deletions
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35
9/src/main.rs
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@ -115,42 +115,21 @@ impl DiskMap {
fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
let mut map = DiskMap::from(input);
let mut i = map.map.len() - 1;
while i != 0 {
// find start index of 'file'
if map.map[i] == Unit::Free {
i -= 1;
continue;
};
let mut len = 1;
while i >= 1 && map.map[i] == map.map[i - 1] {
i -= 1;
len += 1;
}
let file_id = match map.map[i] {
Unit::File(id) => id,
_ => panic!(),
};
for file in map.files.iter().rev() {
let frees = map
.map
.iter()
.enumerate()
.take(i + len + 1)
.filter(|(_i, u)| **u == Unit::Free || **u == Unit::File(file_id))
.take(file.pos + file.len as usize + 1)
.filter(|(_i, u)| **u == Unit::Free || **u == Unit::File(file.id))
.map(|(i, _u)| i)
.take(len)
.take(file.len as usize)
.collect_vec();
if frees[0] >= i {
if i > 0 {
i -= 1;
}
if frees[0] >= file.pos {
continue;
}
for j in 0..len {
map.map.swap(frees[j], i + j);
}
if i > 0 {
i -= 1;
for j in 0..file.len as usize {
map.map.swap(frees[j], file.pos + j);
}
}
map.checksum()