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|
type Block = u32;
type FSunpacked = Vec<Option<Block>>;
fn parse_input(input: &str) -> FSunpacked {
let mut result = vec![];
let mut is_empty = false;
let mut blockid = 0;
for c in input.chars() {
let Some(nblocks) = c.to_digit(10) else {
continue;
};
if is_empty {
for _i in 0..nblocks {
result.push(None);
}
} else {
for _i in 0..nblocks {
result.push(Some(blockid));
}
blockid += 1;
}
is_empty = !is_empty;
}
result
}
fn compact(v: &mut FSunpacked) {
let mut i_empty = 0;
let mut i_full = v.len() - 1;
'out: loop {
while v[i_empty].is_some() {
i_empty += 1;
if i_full < i_empty {
break 'out;
}
}
while v[i_full].is_none() {
i_full -= 1;
if i_full < i_empty {
break 'out;
}
}
(v[i_empty], v[i_full]) = (v[i_full], v[i_empty]);
}
}
fn checksum(v: FSunpacked) -> u64 {
v.into_iter()
.enumerate()
.map(|(i, b)| i as u64 * b.unwrap_or_default() as u64)
.sum()
}
fn p1(input: &str) -> String {
let mut unpacked = parse_input(input);
// println!("{unpacked:?}");
compact(&mut unpacked);
// println!("{unpacked:?}");
let result = checksum(unpacked);
result.to_string()
}
type FSpacked = Vec<(Option<Block>, u32)>;
fn parse_input2(input: &str) -> FSpacked {
let mut result = vec![];
let mut is_empty = false;
let mut blockid = 0;
for c in input.chars() {
// println!("Parsing {c}...");
let Some(nblocks) = c.to_digit(10) else {
continue;
};
if is_empty {
result.push((None, nblocks));
} else {
result.push((Some(blockid), nblocks));
blockid += 1;
}
is_empty = !is_empty;
}
result
}
fn compact2(v: &mut FSpacked) {
let mut i_empty = 0;
let mut i_full = v.len() - 1;
loop {
while v[i_empty].0.is_some() {
i_empty += 1;
}
while v[i_full].0.is_none() {
i_full -= 1;
}
let fblocks = v[i_full].1;
let mut j_empty = i_empty;
while j_empty <= i_full {
// println!("Can we move {:?} into {:?}?", v[i_full], v[j_empty]);
match v[j_empty] {
(None, eblocks) if eblocks >= fblocks => {
let diff = eblocks - fblocks;
v[j_empty] = v[i_full];
v[i_full] = (None, fblocks);
if diff != 0 {
i_full += 1;
j_empty += 1;
v.insert(j_empty, (None, diff));
}
break;
}
_ => (),
}
j_empty += 1;
}
if i_full == 0 {
break;
} else {
i_full -= 1;
}
}
}
fn unpack(v: &FSpacked) -> FSunpacked {
v.iter()
.flat_map(|(x, count)| (0..*count).map(|_| *x))
.collect()
}
fn p2(input: &str) -> String {
let mut packed = parse_input2(input);
compact2(&mut packed);
let unpacked = unpack(&packed);
// println!("{unpacked:?}");
let result = checksum(unpacked);
result.to_string()
}
fn main() {
aoc2024::run_day("9", p1, p2);
}
|
