real nap

go.mod

@@ -0,0 +1,8 @@
+module git.jxs.me/r/knapsack
+
+go 1.20
+
+require (
+	github.com/carlmjohnson/be v0.23.1
+	golang.org/x/exp v0.0.0-20230817173708-d852ddb80c63
+)

go.sum

@@ -0,0 +1,4 @@
+github.com/carlmjohnson/be v0.23.1 h1:lmzkNRv25/mptDQ1ywXMvgQ6u6IZMYna/KHWAquM1II=
+github.com/carlmjohnson/be v0.23.1/go.mod h1:KAgPUh0HpzWYZZI+IABdo80wTgY43YhbdsiLYAaSI/Q=
+golang.org/x/exp v0.0.0-20230817173708-d852ddb80c63 h1:m64FZMko/V45gv0bNmrNYoDEq8U5YUhetc9cBWKS1TQ=
+golang.org/x/exp v0.0.0-20230817173708-d852ddb80c63/go.mod h1:0v4NqG35kSWCMzLaMeX+IQrlSnVE/bqGSyC2cz/9Le8=

main.go

@@ -0,0 +1,54 @@
+package main
+
+import "golang.org/x/exp/constraints"
+
+type Book struct {
+	Weight uint
+	Value  uint
+}
+
+func MaxValue(capacity uint, books []Book) uint {
+	if capacity == 0 {
+		return 0
+	}
+	if len(books) == 0 {
+		return 0
+	}
+
+	book := books[0]
+	return Max(
+		book.Value+MaxValue(capacity-book.Weight, books[1:]),
+		MaxValue(capacity, books[1:]),
+	)
+
+}
+
+func main() {
+	println("Did it")
+}
+func Max[T constraints.Ordered](args ...T) T {
+	if len(args) == 0 {
+		return *new(T) // zero value of T
+	}
+
+	if isNan(args[0]) {
+		return args[0]
+	}
+
+	max := args[0]
+	for _, arg := range args[1:] {
+
+		if isNan(arg) {
+			return arg
+		}
+
+		if arg > max {
+			max = arg
+		}
+	}
+	return max
+}
+
+func isNan[T constraints.Ordered](arg T) bool {
+	return arg != arg
+}

main_test.go

@@ -0,0 +1,37 @@
+package main_test
+
+import (
+	"testing"
+
+	ks "git.jxs.me/r/knapsack"
+
+	"github.com/carlmjohnson/be"
+)
+
+func TestDefaultsZero(t *testing.T) {
+	result := ks.MaxValue(0, []ks.Book{})
+	be.Equal(t, 0, result)
+}
+
+func TestFitsOne(t *testing.T) {
+	result := ks.MaxValue(1, []ks.Book{{Weight: 1, Value: 2}})
+	be.Equal(t, 2, result)
+}
+
+func TestFitsHigher(t *testing.T) {
+	result := ks.MaxValue(1, []ks.Book{
+		{Weight: 1, Value: 2},
+		{Weight: 1, Value: 3},
+	})
+	be.Equal(t, 3, result)
+}
+
+func TestPrefersMultiple(t *testing.T) {
+	result := ks.MaxValue(3, []ks.Book{
+		{Weight: 3, Value: 4},
+		{Weight: 1, Value: 1},
+		{Weight: 1, Value: 2},
+		{Weight: 1, Value: 3},
+	})
+	be.Equal(t, 6, result)
+}