Data commit

Task/Knapsack-problem-Bounded/Go/knapsack-problem-bounded.go

@@ -0,0 +1,99 @@
+package main
+
+import "fmt"
+
+type Item struct {
+	name               string
+	weight, value, qty int
+}
+
+var items = []Item{
+	{"map",			9,	150,	1},
+	{"compass",		13,	35,	1},
+	{"water",		153,	200,	2},
+	{"sandwich",		50,	60,	2},
+	{"glucose",		15,	60,	2},
+	{"tin",			68,	45,	3},
+	{"banana",		27,	60,	3},
+	{"apple",		39,	40,	3},
+	{"cheese",		23,	30,	1},
+	{"beer",		52,	10,	3},
+	{"suntancream",		11,	70,	1},
+	{"camera",		32,	30,	1},
+	{"T-shirt",		24,	15,	2},
+	{"trousers",		48,	10,	2},
+	{"umbrella",		73,	40,	1},
+	{"w-trousers",		42,	70,	1},
+	{"w-overclothes",	43,	75,	1},
+	{"note-case",		22,	80,	1},
+	{"sunglasses",		7,      20,	1},
+	{"towel",		18,	12,	2},
+	{"socks",		4,      50,	1},
+	{"book",		30,	10,	2},
+}
+
+type Chooser struct {
+	Items []Item
+	cache map[key]solution
+}
+
+type key struct {
+	w, p int
+}
+
+type solution struct {
+	v, w int
+	qty  []int
+}
+
+func (c Chooser) Choose(limit int) (w, v int, qty []int) {
+	c.cache = make(map[key]solution)
+	s := c.rchoose(limit, len(c.Items)-1)
+	c.cache = nil // allow cache to be garbage collected
+	return s.v, s.w, s.qty
+}
+
+func (c Chooser) rchoose(limit, pos int) solution {
+	if pos < 0 || limit <= 0 {
+		return solution{0, 0, nil}
+	}
+
+	key := key{limit, pos}
+	if s, ok := c.cache[key]; ok {
+		return s
+	}
+
+	best_i, best := 0, solution{0, 0, nil}
+	for i := 0; i*items[pos].weight <= limit && i <= items[pos].qty; i++ {
+		sol := c.rchoose(limit-i*items[pos].weight, pos-1)
+		sol.v += i * items[pos].value
+		if sol.v > best.v {
+			best_i, best = i, sol
+		}
+	}
+
+	if best_i > 0 {
+		// best.qty is used in another cache entry,
+		// we need to duplicate it before modifying it to
+		// store as our cache entry.
+		old := best.qty
+		best.qty = make([]int, len(items))
+		copy(best.qty, old)
+		best.qty[pos] = best_i
+		best.w += best_i * items[pos].weight
+	}
+	c.cache[key] = best
+	return best
+}
+
+func main() {
+	v, w, s := Chooser{Items: items}.Choose(400)
+
+	fmt.Println("Taking:")
+	for i, t := range s {
+		if t > 0 {
+			fmt.Printf("  %d of %d %s\n", t, items[i].qty, items[i].name)
+		}
+	}
+	fmt.Printf("Value: %d; weight: %d\n", v, w)
+}