Create dynamic knapsack algo

Attempt to liberate the best combination of items from a house you're
burgling with a knapsack weight constraint for the highest value.

- Considering the items weights & values; traverse vertically through a
  matrix (2d array) of sub-problems to find the optimal combination of
  items to boost.

Author: travisjupp

dynamicKnapsack.js

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+const dynamicKnapsack = function(weightCap, weights, values) {
+  const numItem = weights.length;
+  const matrix = new Array(numItem);
+
+  for (let index = 0; index <= numItem; index++) {
+    matrix[index] = new Array(weightCap + 1);
+    for (let weight = 0; weight <= weightCap; weight++) {
+      if (index === 0 || weight === 0) {
+        matrix[index][weight] = 0;
+        // else if the weight of element at index - 1 <= weight:
+      } else if (weights[index-1] <= weight) {
+        // find possible values of including and excluding the item
+        const prevItemsValue = matrix[index - 1][weight];
+        const currItemsWeight = weights[index - 1];
+        const currItemsValue = values[index - 1];
+        const availWeight = weight - currItemsWeight;
+        const prevItems = matrix
+          .map((item, i) => {
+            // return prev item values without overflowing knapsack
+            return item[availWeight]
+              && i !== index // Exclude current items row
+              ? item[availWeight]
+              : 0
+          });
+
+        console.log('ROW:', index, 'COL:', weight, 'currItemsValue:',
+          currItemsValue, '\n', 'prevItems (avail):', prevItems, 'MAX:',
+          prevItems.reduce((a, b) => {return Math.max(a, b)}, -Infinity),
+          '\n',);
+
+        // set element at [index][weight] to max of those values
+        matrix[index][weight] = Math.max(
+          prevItemsValue,
+          currItemsValue,
+          prevItems.reduce(
+            (a, b) => {
+              return Math.max(a, b)
+            }, -Infinity) + currItemsValue
+        )
+
+      } else { // item weight > weight
+        // set element at [index][weight] to element one above
+        matrix[index][weight] = matrix[index-1][weight];
+      }
+    }
+  }
+  console.log('=>', matrix[numItem][weightCap]);
+  return matrix[numItem][weightCap];
+};
+
+export default dynamicKnapsack;
+

dynamicKnapsack.test.js

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+// import {describe, it} from 'node:test';
+import assert from 'node:assert/strict';
+import {jest} from '@jest/globals';
+import util from 'node:util';
+import {style} from './styles.js';
+util.inspect.defaultOptions.depth = null; // show full objects
+// util.inspect.defaultOptions.depth = 0; // show truncated objects
+util.inspect.defaultOptions.compact = true; // dont break objects to new lines
+// util.inspect.defaultOptions.compact = false; // break objects to new lines
+
+// suppress jests tracing console logs
+import console from 'console';
+const jestConsole = console;
+import knapsack from './dynamicKnapsack.js';
+
+beforeEach(() => {
+  global.console = console;
+  console.log(style.color(255,0,255),'▷',style.reset,style.color(39),expect.getState().currentTestName,style.reset,'\n'); });
+
+afterEach(() => {
+  global.console = jestConsole;
+  console.log(style.color(99), style.hr.double, style.reset);
+});
+
+describe('dynamicKnapsack', () => {
+  it('should return optimal value (7 items)', () => {
+    const weightCap = 50;
+    const weights = [31, 10, 20, 19, 4, 3, 6];
+    const values = [70, 20, 39, 37, 7, 5, 10];
+    expect(knapsack(weightCap, weights, values))
+      .toBe(107);
+  });
+
+  it('should return optimal value (5 items)', () => {
+    const weightCap = 5;
+    const weights = [1, 3, 5];
+    const values = [250, 300, 500];
+    expect(knapsack(weightCap, weights, values))
+      .toBe(550);
+  });
+
+});
+