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05.rs
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05.rs
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#![feature(test)]
advent_of_code_2023::solution!(5);
use std::ops::Range;
use nom::{
bytes::complete::{tag, take_while},
character::complete::{alpha1, newline, space1},
combinator::map_res,
multi::{count, separated_list0},
sequence::tuple,
IResult,
};
pub fn part_1(input: &str) -> Option<i64> {
let (input, (seeds, maps)) = parse_input(input, parse_seed_list).unwrap();
assert_eq!(input, "");
let locations = seeds
.iter()
.map(|seed| maps.iter().fold(*seed, |acc, m| m.transform_value(acc)));
locations.min()
}
pub fn part_2(input: &str) -> Option<i64> {
let (input, (seeds, maps)) = parse_input(input, parse_seed_range_list).unwrap();
assert_eq!(input, "");
let mut ranges = seeds;
let mut transformed_seed_ranges = Vec::new();
for map in maps {
for range in &ranges {
transformed_seed_ranges.extend(map.transform_range(range))
}
std::mem::swap(&mut ranges, &mut transformed_seed_ranges);
transformed_seed_ranges.clear();
}
ranges.sort_by_key(|r| r.start);
Some(ranges[0].start)
}
#[derive(Debug)]
struct Map(Vec<MapRange>);
impl Map {
pub fn new(mut ranges: Vec<MapRange>) -> Self {
ranges.sort_by_key(|r| r.src_range.start);
Self(ranges)
}
pub fn transform_value(&self, value: i64) -> i64 {
for range in &self.0 {
if !range.contains_value(value) {
continue;
}
let offset = range.dest_range.start - range.src_range.start;
return value + offset;
}
value
}
/// Uses the rules of the map to transform a range to one or more new ranges
pub fn transform_range(&self, input_range: &Range<i64>) -> Vec<Range<i64>> {
let mut result_ranges = Vec::new();
// Create sorted list of ranges that are relevant to the input (partially or fully cover the input)
let relevant_ranges: Vec<_> = self
.0
.iter()
.filter(|mr| mr.partially_covers_range(input_range))
.collect();
// If this map does not cover any parts of the input range, we can just return the input range
if relevant_ranges.is_empty() {
return vec![input_range.clone()];
}
let mut current_range = input_range.clone();
for relevant_range in relevant_ranges {
// Start of current range is not covered by this range
// Current Range: |--------------|
// Relevant Range: |-----|
if current_range.start < relevant_range.src_range.start {
result_ranges.push(current_range.start..relevant_range.src_range.start);
current_range.start = relevant_range.src_range.start;
}
// Current range is fully contained within this relevant range (end case)
// Current Range: |------|
// Relevant Range: |----------|
// or
// Current Range: |----|
// Relevant Range: |----------|
if relevant_range.src_range.end > current_range.end {
result_ranges.push(
relevant_range.map_value(current_range.start)
..relevant_range.map_value(current_range.end - 1) + 1,
);
current_range.start = current_range.end;
break;
}
// Relevant range covers part of the start of the current range
// Current Range: |------------|
// Relevant Range: |-----| ...
// or
// Current Range: |----------|
// Relevant Range: |-----| ...
if relevant_range.src_range.end < current_range.end {
result_ranges.push(
relevant_range.map_value(current_range.start)
..relevant_range.map_value(relevant_range.src_range.end - 1) + 1,
);
current_range.start = relevant_range.src_range.end;
continue;
}
// Current range end lines up with relevant range end
// Current Range: |----|
// Relevant Range: |------|
// or
// Current Range: |------|
// Relevant Range: |------|
if relevant_range.src_range.end == current_range.end {
result_ranges.push(
relevant_range.map_value(current_range.start)
..relevant_range.map_value(current_range.end - 1) + 1,
);
current_range.start = current_range.end;
break;
}
}
if current_range.start != current_range.end {
result_ranges.push(current_range);
}
result_ranges
}
}
#[derive(Debug)]
struct MapRange {
dest_range: Range<i64>,
src_range: Range<i64>,
}
impl MapRange {
pub fn new(dest_range_start: i64, src_range_start: i64, range_length: i64) -> Self {
Self {
dest_range: dest_range_start..dest_range_start + range_length,
src_range: src_range_start..src_range_start + range_length,
}
}
pub fn contains_value(&self, value: i64) -> bool {
self.src_range.contains(&value)
}
pub fn map_value(&self, value: i64) -> i64 {
if !self.contains_value(value) {
return value;
}
let offset = self.dest_range.start - self.src_range.start;
value + offset
}
pub fn partially_covers_range(&self, range: &Range<i64>) -> bool {
range.end >= self.src_range.start && range.start <= self.src_range.end
}
}
fn parse_input<T>(
input: &str,
seed_parsing_fn: fn(&str) -> IResult<&str, T>,
) -> IResult<&str, (T, Vec<Map>)> {
let (input, seeds) = seed_parsing_fn(input)?;
let (input, _) = count(newline, 2)(input)?;
let (input, maps) = separated_list0(count(newline, 2), parse_map)(input)?;
Ok((input, (seeds, maps)))
}
fn parse_seed_list(input: &str) -> IResult<&str, Vec<i64>> {
let (input, _) = tag("seeds: ")(input)?;
let (input, seeds) = separated_list0(space1, parse_int)(input)?;
Ok((input, seeds))
}
fn parse_seed_range_list(input: &str) -> IResult<&str, Vec<Range<i64>>> {
let (input, _) = tag("seeds: ")(input)?;
let (input, seeds) = separated_list0(space1, tuple((parse_int, space1, parse_int)))(input)?;
let seeds = seeds
.iter()
.map(|(start, _, length)| *start..(start + length))
.collect::<Vec<_>>();
Ok((input, seeds))
}
fn parse_map(input: &str) -> IResult<&str, Map> {
let (input, _) = tuple((alpha1, tag("-to-"), alpha1, tag(" map:"), newline))(input)?;
let (input, ranges) = separated_list0(newline, parse_map_range)(input)?;
Ok((input, Map::new(ranges)))
}
fn parse_map_range(input: &str) -> IResult<&str, MapRange> {
let (input, (dest_range_start, _, src_range_start, _, range_length)) =
tuple((parse_int, space1, parse_int, space1, parse_int))(input)?;
Ok((
input,
MapRange::new(dest_range_start, src_range_start, range_length),
))
}
fn parse_int(input: &str) -> IResult<&str, i64> {
map_res(take_while(|c: char| c.is_ascii_digit()), str::parse)(input)
}