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|
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
}
|
