Solve day 5 part 1

src/bin/05.rs

@@ -0,0 +1,126 @@
+use itertools::Itertools;
+
+const INPUT: &str = include_str!("../../input/05");
+const TEST_INPUT: &str = include_str!("../../input/05-test");
+
+fn main() {
+    assert_eq!(part1(TEST_INPUT), 35);
+    println!("Part 1: {}", part1(INPUT));
+    assert_eq!(part2(TEST_INPUT), 46);
+    println!("Part 2: {}", part2(INPUT));
+}
+
+fn part1(input: &str) -> u64 {
+    let garden = Garden::parse(input);
+    garden
+        .simple_seeds
+        .iter()
+        .copied()
+        .map(|seed| garden.map(seed))
+        .min()
+        .unwrap()
+}
+
+fn part2(input: &str) -> u64 {
+    0
+}
+
+#[derive(Debug)]
+struct Garden {
+    simple_seeds: Vec<u64>,
+    seed_ranges: Vec<SeedRange>,
+    maps: Vec<Map>,
+}
+
+impl Garden {
+    fn parse(input: &str) -> Self {
+        let mut blocks = input.split("\n\n");
+        let seeds = blocks.next().unwrap().strip_prefix("seeds: ").unwrap();
+        let maps = blocks.map(Map::parse).collect();
+
+        let simple_seeds = parse_ws_numbers(seeds);
+        let seed_ranges = simple_seeds
+            .iter()
+            .copied()
+            .tuples()
+            .map(|(start, length)| SeedRange { start, length })
+            .collect();
+
+        Self {
+            simple_seeds,
+            seed_ranges,
+            maps,
+        }
+    }
+
+    /// Look up n in every map.
+    fn map(&self, mut n: u64) -> u64 {
+        for map in &self.maps {
+            n = map.map(n);
+        }
+        n
+    }
+}
+
+#[derive(Debug)]
+struct SeedRange {
+    start: u64,
+    length: u64,
+}
+
+#[derive(Debug)]
+struct Map {
+    ranges: Vec<MappedRange>,
+}
+
+impl Map {
+    fn map(&self, n: u64) -> u64 {
+        for range in &self.ranges {
+            if let Some(mapped) = range.map(n) {
+                return mapped;
+            }
+        }
+
+        n
+    }
+
+    fn parse(block: &str) -> Self {
+        let lines = block.lines().skip(1);
+        let ranges = lines.map(MappedRange::parse).collect();
+        Self { ranges }
+    }
+}
+
+#[derive(Debug)]
+struct MappedRange {
+    destination: u64,
+    source: u64,
+    length: u64,
+}
+
+impl MappedRange {
+    fn map(&self, n: u64) -> Option<u64> {
+        let source_start = self.source;
+        let source_end = source_start + self.length;
+        if (source_start..source_end).contains(&n) {
+            Some(n - source_start + self.destination)
+        } else {
+            None
+        }
+    }
+
+    fn parse(line: &str) -> Self {
+        let [destination, source, length] = parse_ws_numbers(line).try_into().unwrap();
+        Self {
+            destination,
+            source,
+            length,
+        }
+    }
+}
+
+fn parse_ws_numbers(s: &str) -> Vec<u64> {
+    s.split_ascii_whitespace()
+        .map(|s| s.parse().unwrap())
+        .collect()
+}