Day 5 Part 2 complete

src/solutions/day05.rs

@@ -22,9 +22,35 @@ impl Solution for Day05 {
 
     fn part2(
         &self,
-        _input: &mut Vec<String>,
+        input: &mut Vec<String>,
     ) -> Result<Box<dyn std::fmt::Display>, Box<dyn std::error::Error>> {
-        Ok(Box::new("Ready"))
+        let (seeds, maps) = self.get_mappings(input)?;
+
+        let seeds = seeds.iter()
+            .tuples()
+            .map(|(&a, len)| (a, a + len))
+            .collect::<Vec<_>>();
+        let locations = maps.iter().fold(seeds, |seeds, mappings|
+            seeds.iter().flat_map(|&(start, end)| {
+            let mut mapped = Vec::new();
+            let mut unmapped = vec![(start, end)];
+            for &(dst, src, len) in mappings {
+                let mut m = Vec::new();
+                for (start, end) in unmapped {
+                let a = (start, end.min(src));
+                let b = (start.max(src), (src+len).min(end));
+                let c = ((src+len).max(start), end);
+                if a.0 < a.1 { m.push(a); }
+                if b.0 < b.1 { mapped.push((b.0-src+dst, b.1-src+dst)); }
+                if c.0 < c.1 { m.push(c); }
+                }
+                unmapped = m;
+            }
+            mapped.extend(unmapped);
+            mapped
+            }).collect()
+        );
+        Ok(Box::new(locations.iter().map(|&(s, _)| s).min().unwrap()))
     }
 
     fn get_day(&self) -> u8 {
@@ -90,6 +116,6 @@ mod test {
             .unwrap()
             .to_string();
 
-        assert_eq!(answer, "Ready");
+        assert_eq!(answer, "46");
     }
 }