dynamic programming!

main.go

@@ -1,13 +1,15 @@
 package main
 
-import "golang.org/x/exp/constraints"
+import (
+	"golang.org/x/exp/constraints"
+)
 
 type Book struct {
-	Weight uint
-	Value  uint
+	Weight int
+	Value  int
 }
 
-func MaxValue(capacity uint, books []Book) uint {
+func MaxValue(capacity int, books []Book) int {
 	if capacity == 0 {
 		return 0
 	}
@@ -25,6 +27,21 @@ func MaxValue(capacity uint, books []Book) uint {
 	return Max(withBook, withoutBook)
 }
 
+func DynamicMaxValue(capacity int, books []Book) int {
+	memo := make([]int, capacity+1)
+
+	for _, book := range books {
+		for c := capacity; c >= 0; c-- {
+			if book.Weight <= c {
+				memo[c] = Max(memo[c], memo[c-book.Weight]+book.Value)
+			}
+		}
+	}
+
+	return memo[capacity]
+
+}
+
 func main() {
 	println("Did it")
 }

main_test.go

@@ -13,6 +13,11 @@ func TestDefaultsZero(t *testing.T) {
 	be.Equal(t, 0, result)
 }
 
+func TestEmpty(t *testing.T) {
+	result := ks.DynamicMaxValue(1, []ks.Book{})
+	be.Equal(t, 0, result)
+}
+
 func TestFitsOne(t *testing.T) {
 	result := ks.MaxValue(1, []ks.Book{
 		{Weight: 1, Value: 2},
@@ -45,3 +50,48 @@ func TestIgnoresTooBig(t *testing.T) {
 	})
 	be.Equal(t, 1, result)
 }
+
+// Dynamic
+
+func TestDynamicDefaultsZero(t *testing.T) {
+	result := ks.DynamicMaxValue(0, []ks.Book{})
+	be.Equal(t, 0, result)
+}
+
+func TestDynamicFitsOne(t *testing.T) {
+	result := ks.DynamicMaxValue(1, []ks.Book{
+		{Weight: 1, Value: 2},
+	})
+	be.Equal(t, 2, result)
+}
+
+func TestDynamicFitsHigher(t *testing.T) {
+	result := ks.DynamicMaxValue(1, []ks.Book{
+		{Weight: 1, Value: 3},
+		{Weight: 1, Value: 2},
+	})
+	be.Equal(t, 3, result)
+}
+
+func TestDynamicPrefersMultiple(t *testing.T) {
+	result := ks.DynamicMaxValue(3, []ks.Book{
+		{Weight: 3, Value: 4},
+		{Weight: 1, Value: 1},
+		{Weight: 1, Value: 2},
+		{Weight: 1, Value: 3},
+	})
+	be.Equal(t, 6, result)
+}
+
+func TestDynamicIgnoresTooBig(t *testing.T) {
+	result := ks.DynamicMaxValue(1, []ks.Book{
+		{Weight: 10, Value: 4},
+		{Weight: 1, Value: 1},
+	})
+	be.Equal(t, 1, result)
+}
+
+func TestDynamicEmpty(t *testing.T) {
+	result := ks.DynamicMaxValue(1, []ks.Book{})
+	be.Equal(t, 0, result)
+}