Added knapsack in Golang

dynamic_programing/knapsack_problem/go/knapsack.go

@@ -0,0 +1,64 @@
+package knapsack
+
+type Packable interface {
+	Weight() int64
+	Value() int64
+}
+
+func Knapsack(items []Packable, capacity int64) []int64 {
+
+	values := make([][]int64, len(items)+1)
+	for i := range values {
+		values[i] = make([]int64, capacity+1)
+	}
+
+	keep := make([][]int, len(items)+1)
+	for i := range keep {
+		keep[i] = make([]int, capacity+1)
+	}
+
+	for i := int64(0); i < capacity+1; i++ {
+		values[0][i] = 0
+		keep[0][i] = 0
+	}
+
+	for i := 0; i < len(items)+1; i++ {
+		values[i][0] = 0
+		keep[i][0] = 0
+	}
+
+	for i := 1; i <= len(items); i++ {
+		for c := int64(1); c <= capacity; c++ {
+
+			itemFits := (items[i-1].Weight() <= c)
+			if !itemFits {
+				continue
+			}
+
+			maxValueAtThisCapacity := items[i-1].Value() + values[i-1][c-items[i-1].Weight()]
+			previousValueAtThisCapacity := values[i-1][c]
+
+			if itemFits && (maxValueAtThisCapacity > previousValueAtThisCapacity) {
+				values[i][c] = maxValueAtThisCapacity
+				keep[i][c] = 1
+			} else {
+				values[i][c] = previousValueAtThisCapacity
+				keep[i][c] = 0
+			}
+		}
+	}
+
+	n := len(items)
+	c := capacity
+	var indices []int64
+
+	for n > 0 {
+		if keep[n][c] == 1 {
+			indices = append(indices, int64(n-1))
+			c -= items[n-1].Weight()
+		}
+		n--
+	}
+
+	return indices
+}

dynamic_programing/knapsack_problem/go/knapsack_test.go

@@ -0,0 +1,80 @@
+package knapsack
+
+import (
+	"testing"
+)
+
+type TestKnapsackItem struct {
+	weight int64
+	value  int64
+}
+
+func (i TestKnapsackItem) Weight() int64 {
+	return i.weight
+}
+
+func (i TestKnapsackItem) Value() int64 {
+	return i.value
+}
+
+func TestKnapsackEasy(t *testing.T) {
+	items := []Packable{
+		TestKnapsackItem{
+			3, 5,
+		},
+		TestKnapsackItem{
+			2, 3,
+		},
+		TestKnapsackItem{
+			1, 4,
+		},
+	}
+
+	indices := Knapsack(items, 5)
+	var value int64
+	for _, i := range indices {
+		value += items[i].Value()
+	}
+
+	if value != 9 {
+		t.Errorf("Expected %d, got %d", 9, value)
+	}
+}
+
+func TestZeroCapacityKnapsack(t *testing.T) {
+	items := []Packable{
+		TestKnapsackItem{
+			3, 5,
+		},
+		TestKnapsackItem{
+			2, 3,
+		},
+		TestKnapsackItem{
+			1, 4,
+		},
+	}
+
+	indices := Knapsack(items, 0)
+	var value int64
+	for _, i := range indices {
+		value += items[i].Value()
+	}
+
+	if value != 0 {
+		t.Errorf("Expected %d, got %d", 0, value)
+	}
+}
+
+func TestNoItemsForKnapsack(t *testing.T) {
+	items := []Packable{}
+
+	indices := Knapsack(items, 0)
+	var value int64
+	for _, i := range indices {
+		value += items[i].Value()
+	}
+
+	if value != 0 {
+		t.Errorf("Expected %d, got %d", 0, value)
+	}
+}