1 files changed, 142 insertions, 0 deletions
diff --git a/aoc23/day05_test.go b/aoc23/day05_test.go
new file mode 100644
index 0000000..4b07a76
--- /dev/null
+++ b/aoc23/day05_test.go
@@ -0,0 +1,142 @@
+package aoc23
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"strings"
+	"testing"
+)
+
+type Almanac struct {
+	seeds    []Range
+	mappings [][]Mapping
+}
+
+func (a *Almanac) Resolve(n int) int {
+	for _, rs := range a.mappings {
+		for _, r := range rs {
+			if found, ok := r.Target(n); ok {
+				n = found
+				break
+			}
+		}
+	}
+	return n
+}
+
+type Mapping struct {
+	src  int
+	dst  int
+	size int
+}
+
+func (r Mapping) Target(n int) (int, bool) {
+	if n >= r.src && n <= r.src+r.size {
+		return r.dst + (n - r.src), true
+	}
+	return 0, false
+}
+
+type Range struct{ start, end int }
+
+func (r Range) Each(f func(int)) {
+	for i := r.start; i <= r.end; i++ {
+		f(i)
+	}
+}
+
+func parseMapping(s string) Mapping {
+	parts := strings.Fields(s)
+	if got, want := len(parts), 3; got != want {
+		panic(fmt.Sprintf("got %d fields in %q, want %d", got, s, want))
+	}
+	ints := transform(parts, atoi)
+	return Mapping{src: ints[1], dst: ints[0], size: ints[2]}
+}
+
+func parseAlmanac(r io.Reader, seedRange bool) Almanac {
+	var (
+		seeds    []Range
+		mappings [][]Mapping
+	)
+	mappingIdx := -1
+	parseLines(r, func(line string) string {
+		if strings.HasPrefix(line, "seeds:") {
+			parts := strings.Fields(line)
+			ints := transform(parts[1:], atoi)
+			if seedRange {
+				for i := 0; i < len(ints); i += 2 {
+					start := ints[i]
+					end := start + ints[i+1]
+					seeds = append(seeds, Range{start, end})
+				}
+			} else {
+				for _, seed := range ints {
+					seeds = append(seeds, Range{seed, seed})
+				}
+			}
+		} else if strings.HasSuffix(line, "map:") {
+			mappings = append(mappings, []Mapping{})
+			mappingIdx++
+		} else if mappingIdx > -1 && line != "" {
+			mappings[mappingIdx] = append(mappings[mappingIdx], parseMapping(line))
+		}
+		return ""
+	})
+	return Almanac{seeds, mappings}
+}
+
+func locationNumber(r io.Reader, seedRange bool) int {
+	a := parseAlmanac(r, seedRange)
+	best := math.MaxInt
+	for _, seed := range a.seeds {
+		seed.Each(func(n int) {
+			best = min(best, a.Resolve(n))
+		})
+	}
+	return best
+}
+
+func TestDay05(t *testing.T) {
+	example := `
+seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+temperature-to-humidity map:
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4
+`
+	assert(t, 35, run(partial(locationNumber, false), inputString(example)))
+	assert(t, 424490994, run(partial(locationNumber, false), inputFile(5)))
+
+	assert(t, 46, run(partial(locationNumber, true), inputString(example)))
+	assert(t, 15290096, run(partial(locationNumber, true), inputFile(5))) // Correct, but terribly slow
+}