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62 lines
2 KiB
Rust
62 lines
2 KiB
Rust
use std::{cmp, ops::Range};
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pub fn part2(input: &str) -> u64 {
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let mut lines = input.lines();
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let seeds = lines
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.next()
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.unwrap()
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.strip_prefix("seeds: ")
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.unwrap()
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.split_ascii_whitespace()
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.map(|n| n.parse::<u64>().unwrap())
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.collect::<Vec<_>>();
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let seeds = seeds.chunks(2);
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let maps = super::parse_maps(lines);
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let mut min_loc = u64::MAX;
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let mut current_seeds: Vec<(usize, usize, Range<u64>)> = seeds
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.map(|seed| (0, 0, seed[0]..(seed[0] + seed[1])))
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.collect();
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'queue: while let Some((stage, range_idx, numbers)) = current_seeds.pop() {
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if stage == maps.len() {
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// Range is done.
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min_loc = cmp::min(min_loc, numbers.start);
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continue;
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}
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let ranges = &maps[stage];
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for range in ranges.iter().skip(range_idx) {
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if range.source_end() <= numbers.start || range.source_start >= numbers.end {
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// Completely out of range.
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continue;
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}
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// Part that falls before this redirection, needs to be queued again.
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let pre = numbers.start..range.source_start;
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let in_ = cmp::max(numbers.start, range.source_start)
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..cmp::min(numbers.end, range.source_end());
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let post = range.source_end()..(numbers.end);
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if !pre.is_empty() {
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current_seeds.push((stage, range_idx + 1, pre));
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}
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if !post.is_empty() {
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current_seeds.push((stage, range_idx + 1, post));
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}
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let offset = in_.start - range.source_start;
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let new =
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(range.dest_start + offset)..(range.dest_start + offset + (in_.end - in_.start));
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if !new.is_empty() {
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current_seeds.push((stage + 1, 0, new));
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}
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continue 'queue;
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}
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// No change, pass unaffected
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current_seeds.push((stage + 1, 0, numbers));
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}
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min_loc
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}
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