Beginner Exercism • javascript

Change

Challenge Overview

Determine the fewest number of coins to give a customer so that the sum of their values equals the correct amount of change.

Introduction

In the mystical village of Coinholt, you stand behind the counter of your bakery, arranging a fresh batch of pastries. The door creaks open, and in walks Denara, a skilled merchant with a keen eye for quality goods. After a quick meal, she slides a shimmering coin across the counter, representing a value of 100 units.

You smile, taking the coin, and glance at the total cost of the meal: 88 units. That means you need to return 12 units in change.

Denara holds out her hand expectantly. “Just give me the fewest coins,” she says with a smile. “My pouch is already full, and I don’t want to risk losing them on the road.”

You know you have a few options. “We have Lumis (worth 10 units), Viras (worth 5 units), and Zenth (worth 2 units) available for change.”

You quickly calculate the possibilities in your head:

one Lumis (1 × 10 units) + one Zenth (1 × 2 units) = 2 coins total
two Viras (2 × 5 units) + one Zenth (1 × 2 units) = 3 coins total
six Zenth (6 × 2 units) = 6 coins total

“The best choice is two coins: one Lumis and one Zenth,” you say, handing her the change.

Denara smiles, clearly impressed. “As always, you’ve got it right.”

Instructions

Determine the fewest number of coins to give a customer so that the sum of their values equals the correct amount of change.

Examples

An amount of 15 with available coin values [1, 5, 10, 25, 100] should return one coin of value 5 and one coin of value 10, or [5, 10].
An amount of 40 with available coin values [1, 5, 10, 25, 100] should return one coin of value 5, one coin of value 10, and one coin of value 25, or [5, 10, 25].

Community Solutions

View Community Solutions

The following are the top 3 community solutions by stars:

Solution 1 by @gmurph91 (⭐ 6) — View on Exercism
Solution 2 by @anurat (⭐ 0) — View on Exercism
Solution 3 by @em1lra3v (⭐ 0) — View on Exercism

Source: Exercism javascript/change

💡 View Solution

export class Change {
  calculate(coinArray, target) {
    if (target < 0) {
      throw 'Negative totals are not allowed.';
    }
    const change = [[]];
    for (let i = 0; i < target; ++i) {
      if (!change[i]) continue;
      coinArray.forEach(c => {
        const cs = [...change[i], c];