fix unbound knapsack problem with items more than 1(default value) (trekhleb#73)

Author: shsina

src/algorithms/sets/knapsack-problem/Knapsack.js

@@ -165,7 +165,10 @@ export default class Knapsack {
  const availableWeight = this.weightLimit - this.totalWeight;
  const maxPossibleItemsCount = Math.floor(availableWeight / currentItem.weight);
 
- if (maxPossibleItemsCount) {
+ if (maxPossibleItemsCount > currentItem.itemsInStock) {
+ currentItem.quantity = currentItem.itemsInStock;
+ this.selectedItems.push(currentItem);
+ } else if (maxPossibleItemsCount) {
  currentItem.quantity = maxPossibleItemsCount;
  this.selectedItems.push(currentItem);
  }

src/algorithms/sets/knapsack-problem/__test__/Knapsack.test.js

@@ -96,6 +96,31 @@ describe('Knapsack', () => {
  new KnapsackItem({ value: 20, weight: 2 }), // v/w ratio is 10
  ];
 
+ const maxKnapsackWeight = 15;
+
+ const knapsack = new Knapsack(possibleKnapsackItems, maxKnapsackWeight);
+
+ knapsack.solveUnboundedKnapsackProblem();
+
+ expect(knapsack.totalValue).toBe(84 + 20 + 12 + 10 + 5);
+ expect(knapsack.totalWeight).toBe(15);
+ expect(knapsack.selectedItems.length).toBe(5);
+ expect(knapsack.selectedItems[0].toString()).toBe('v84 w7 x 1');
+ expect(knapsack.selectedItems[1].toString()).toBe('v20 w2 x 1');
+ expect(knapsack.selectedItems[2].toString()).toBe('v10 w1 x 1');
+ expect(knapsack.selectedItems[3].toString()).toBe('v12 w3 x 1');
+ expect(knapsack.selectedItems[4].toString()).toBe('v5 w2 x 1');
+ });
+
+ it('should solve unbound knapsack problem with items in stock', () => {
+ const possibleKnapsackItems = [
+ new KnapsackItem({ value: 84, weight: 7, itemsInStock: 3 }), // v/w ratio is 12
+ new KnapsackItem({ value: 5, weight: 2, itemsInStock: 2 }), // v/w ratio is 2.5
+ new KnapsackItem({ value: 12, weight: 3, itemsInStock: 1 }), // v/w ratio is 4
+ new KnapsackItem({ value: 10, weight: 1, itemsInStock: 6 }), // v/w ratio is 10
+ new KnapsackItem({ value: 20, weight: 2, itemsInStock: 8 }), // v/w ratio is 10
+ ];
+
  const maxKnapsackWeight = 17;
 
  const knapsack = new Knapsack(possibleKnapsackItems, maxKnapsackWeight);
@@ -109,4 +134,29 @@ describe('Knapsack', () => {
  expect(knapsack.selectedItems[1].toString()).toBe('v20 w2 x 1');
  expect(knapsack.selectedItems[2].toString()).toBe('v10 w1 x 1');
  });
+
+ it('should solve unbound knapsack problem with items in stock and max weight more than sum of all items', () => {
+ const possibleKnapsackItems = [
+ new KnapsackItem({ value: 84, weight: 7, itemsInStock: 3 }), // v/w ratio is 12
+ new KnapsackItem({ value: 5, weight: 2, itemsInStock: 2 }), // v/w ratio is 2.5
+ new KnapsackItem({ value: 12, weight: 3, itemsInStock: 1 }), // v/w ratio is 4
+ new KnapsackItem({ value: 10, weight: 1, itemsInStock: 6 }), // v/w ratio is 10
+ new KnapsackItem({ value: 20, weight: 2, itemsInStock: 8 }), // v/w ratio is 10
+ ];
+
+ const maxKnapsackWeight = 60;
+
+ const knapsack = new Knapsack(possibleKnapsackItems, maxKnapsackWeight);
+
+ knapsack.solveUnboundedKnapsackProblem();
+
+ expect(knapsack.totalValue).toBe((3 * 84) + (2 * 5) + (1 * 12) + (6 * 10) + (8 * 20));
+ expect(knapsack.totalWeight).toBe((3 * 7) + (2 * 2) + (1 * 3) + (6 * 1) + (8 * 2));
+ expect(knapsack.selectedItems.length).toBe(5);
+ expect(knapsack.selectedItems[0].toString()).toBe('v84 w7 x 3');
+ expect(knapsack.selectedItems[1].toString()).toBe('v20 w2 x 8');
+ expect(knapsack.selectedItems[2].toString()).toBe('v10 w1 x 6');
+ expect(knapsack.selectedItems[3].toString()).toBe('v12 w3 x 1');
+ expect(knapsack.selectedItems[4].toString()).toBe('v5 w2 x 2');
+ });
 });