chore: add day 15

day15/example.txt

@@ -0,0 +1 @@
+rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7

day15/main.go

@@ -0,0 +1,123 @@
+package main
+
+import (
+	"bufio"
+	_ "embed"
+	"fmt"
+	"slices"
+	"strings"
+
+	aoc "go.sour.is/advent-of-code-2023"
+)
+
+var log = aoc.Log
+
+func main() { aoc.MustResult(aoc.Runner(run)) }
+
+type result struct {
+	valuePT1 int
+	valuePT2 int
+}
+
+func (r result) String() string { return fmt.Sprintf("%#v", r) }
+
+func run(scan *bufio.Scanner) (*result, error) {
+	r := &result{}
+
+	var ops []string
+	for scan.Scan() {
+		text := scan.Text()
+		ops = strings.Split(text, ",")
+
+		r.valuePT1 = aoc.Reduce(func(i int, t string, sum int) int {
+			sum += hash(t)
+			return sum
+		}, 0, ops...)
+	}
+
+	var boxen boxes
+
+	boxen = aoc.Reduce(func(i int, op string, b boxes) boxes {
+		return b.Op(op)
+	}, boxen, ops...)
+
+	r.valuePT2 = boxen.Sum()
+
+	log(boxen)
+
+	return r, nil
+}
+
+func hash(s string) int {
+	var sum int
+	for _, a := range s {
+		sum += int(a)
+		sum *= 17
+		sum %= 256
+	}
+
+	return sum
+}
+
+type lens struct {
+	label string
+	value int
+}
+type box []lens
+type boxes [256]box
+
+func (lis boxes) String() string {
+	var buf strings.Builder
+	buf.WriteString("Boxes:\n")
+	for i, b := range lis {
+		if len(b) > 0 {
+			fmt.Fprintf(&buf, "Box %d: %v\n",i, b)
+		}
+	}
+	return buf.String()
+}
+
+func (lis box) String() string {
+	var buf strings.Builder
+	if len(lis) > 0 {
+		buf.WriteString(lis[0].String())
+	}
+	for _, l := range lis[1:] {
+		buf.WriteString(l.String())
+	}
+	return buf.String()
+}
+
+func (l lens) String() string {
+	return fmt.Sprintf("[%s %d]", l.label, l.value)
+}
+
+func (lis boxes) Op(op string) boxes {
+	if a, _, ok := strings.Cut(op, "-"); ok {
+		i := hash(a)
+		pos := slices.IndexFunc(lis[i], func(l lens) bool { return l.label == a })
+		if pos >= 0 {
+			lis[i] = append(lis[i][:pos], lis[i][pos+1:]...)
+		}
+	} else if a, b, ok := strings.Cut(op, "="); ok {
+		i := hash(a)
+		pos := slices.IndexFunc(lis[i], func(l lens) bool { return l.label == a })
+		v := aoc.Atoi(b)
+		if pos == -1 {
+			lis[i] = append(lis[i], lens{a, v})
+		} else {
+			lis[i][pos].value = v
+		}
+	}
+
+	return lis
+}
+func (lis boxes) Sum() int {
+	sum := 0
+	for b := range lis {
+		for s := range lis[b] {
+			sum += (b+1) * (s+1) * lis[b][s].value
+		}
+	}
+	return sum
+}

day15/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"testing"
+
+	_ "embed"
+
+	"github.com/matryer/is"
+)
+
+//go:embed example.txt
+var example []byte
+
+//go:embed input.txt
+var input []byte
+
+func TestExample(t *testing.T) {
+	is := is.New(t)
+	scan := bufio.NewScanner(bytes.NewReader(example))
+
+	result, err := run(scan)
+	is.NoErr(err)
+
+	t.Log(result)
+	is.Equal(result.valuePT1, 1320)
+	is.Equal(result.valuePT2, 145)
+}
+
+func TestSolution(t *testing.T) {
+	is := is.New(t)
+	scan := bufio.NewScanner(bytes.NewReader(input))
+
+	result, err := run(scan)
+	is.NoErr(err)
+
+	t.Log(result)
+	is.Equal(result.valuePT1, 503154)
+	is.Equal(result.valuePT2, 251353)
+}

tools.go

@@ -265,4 +265,11 @@ func Transpose[T any](matrix [][]T) [][]T {
 		}
 	}
 	return m
+}
+
+func Reduce[T, U any](fn func(int, T, U) U, u U, list ...T) U {
+	for i, t := range list {
+		u = fn(i, t, u)
+	} 
+	return u
 }