Unbounded Knapsack in JavaScript

"use strict";
// Unbounded Knapsack in JavaScript
//
// PURPOSE
// Unbounded knapsack maximizes value under a capacity limit while allowing unlimited copies
// of each item.
//
// METHOD
// Process each item and scan capacities upward, allowing the current item to extend states
// already improved by another copy of itself.
//
// COMPLEXITY
// O(n * capacity) time, O(capacity) space; pseudo-polynomial.
//
// CONTRACT
// Positive weights, nonnegative values, capacity >=0. Arrays have matching lengths. Returns
// best value, which must fit signed 32-bit.
// Public APIs infer array lengths except in C, which accepts pointer/length pairs. Vertex
// counts and matrix dimensions remain explicit. Arrays must contain signed 32-bit integers.
// Sorted order, correct tree topology, and caller-owned data-structure invariants are
// preconditions; checking them on every query would change query complexity.
// Scalar and shape checks are included. Value-range checks are included where needed to
// prevent invalid indexing or nontermination. Allocation sizes are capped at 4,000,000
// workspace entries. Arithmetic outside Python raises an error on 32-bit overflow; Python
// uses arbitrary precision. Native allocation failures propagate. In-place outputs may be
// partly updated after arithmetic failure. These are single-threaded, in-memory
// implementations.
//
// LANGUAGE DETAILS
// Node.js 18+: Int32Array inputs and workspaces provide compact integer storage. Automatic
// lengths and checked arithmetic reject values outside signed 32-bit. Invalid inputs or
// overflow throw RangeError.
//
// EXAMPLE
// Expected return: 13.
// Run: node example.js
// Tests for this exact source artifact run before publication. The accompanying source
// archive includes unit cases, runtime results, and source hashes.

function alg_require(valid) { if (!valid) throw new RangeError("invalid algorithm input"); }
function alg_checked(v) { if (!Number.isInteger(v) || v < -2147483648 || v > 2147483647) throw new RangeError("32-bit result overflow"); return v; }
function alg_add(a,b) { return alg_checked(a+b); }
function alg_sub(a,b) { return alg_checked(a-b); }
function alg_mul(a,b) { return alg_checked(a*b); }
function alg_size(n) { alg_require(Number.isInteger(n) && n>=0 && n<=4000000); return n; }

function unbounded_knapsack(weights, values, capacity) {
    alg_require(weights instanceof Int32Array);
    alg_require(values instanceof Int32Array);
    alg_require(Number.isInteger(capacity) && capacity >= -2147483648 && capacity <= 2147483647);
    let n = weights.length;
    alg_require(((n >= 0) && (n <= 1000000)));
    alg_require((weights.length == n));
    alg_require((values.length == n));
    alg_require(((capacity >= 0) && (capacity <= 1000000)));
    for (let alg_i = 0; alg_i < weights.length; alg_i++) {
        let alg_value = weights[alg_i];
        alg_require((alg_value > 0));
    }
    for (let alg_i = 0; alg_i < values.length; alg_i++) {
        let alg_value = values[alg_i];
        alg_require((alg_value >= 0));
    }
    let dp = new Int32Array(alg_size(alg_add(capacity, 1)));
    let i = 0;
    let c = 0;
    while ((i < n)) {
        c = weights[i];
        while ((c <= capacity)) {
            dp[c] = Math.max(dp[c], alg_add(dp[alg_sub(c, weights[i])], values[i]));
            c = alg_add(c, 1);
        }
        i = alg_add(i, 1);
    }
    return dp[capacity];
}

let weights = new Int32Array([2, 3]);
let values = new Int32Array([4, 5]);
let capacity = 7;
let result = unbounded_knapsack(weights, values, capacity);
console.log(result);