cassidoo-may-2022-challenge

receipts.js

let receipts = [
  { name: "Ximena", paid: 45 },
  { name: "Clara", paid: 130 },
  { name: "Ximena", paid: 100 },
  { name: "Cassidy", paid: 140 },
  { name: "Cassidy", paid: 76 },
  { name: "Clara", paid: 29 },
  { name: "Ximena", paid: 20 },
];

const whoOwes = (receipts) => {
  // Restructure the data for convenience. Get the total amounts paid by person as well as the total overall.
  // Example: { total: 540, payments: { Clara: 159, Ximena: 165, Cassidy: 216 } }
  const bill = receipts.reduce(
    (bill, receipt) => {
      if (!bill.payments[receipt.name]) {
        bill.payments[receipt.name] = 0;
      }
      bill.total += receipt.paid;
      bill.payments[receipt.name] += receipt.paid;
      return bill;
    },
    { total: 0, payments: {} }
  );

  // We'll need this to distribute the total payments among the payers.
  const numPeople = Object.keys(bill.payments).length;

  // Sort payments in ascending order to match the expected output (Clara before Ximena). Smaller payments first.
  const paymentsSorted = Object.fromEntries(
    Object.entries(bill.payments).sort(
      ([_name1, payment1], [_name2, payment2]) => payment1 - payment2
    )
  );

  // Find the largest payment. This person is owed money by the remaining people.
  // NOTE: This assumes that there is only one person owed money.
  const maxPayment = {
    name: Object.entries(paymentsSorted)[numPeople - 1][0],
    amount: Object.entries(paymentsSorted)[numPeople - 1][1],
  };

  // The amount each person should've actually paid if it had been distributed evenly
  const evenPaymentPerPerson = bill.total / numPeople;

  // Identify the people who owe money as well as the amounts they owe. Store in an intermediate result
  // for further processing/logging. Example: { Clara: 21, Ximena: 15 }.
  const amountsOwedByName = Object.keys(paymentsSorted).reduce(
    (amountsOwedByName, name) => {
      if (name === maxPayment.name) return amountsOwedByName;
      const amountPaid = bill.payments[name];
      const amountOwed = evenPaymentPerPerson - amountPaid;
      amountsOwedByName[name] = amountOwed;
      return amountsOwedByName;
    },
    {}
  );

  return Object.entries(amountsOwedByName)
    .map(
      ([name, amountOwed]) => `${name} owes ${maxPayment.name} $${amountOwed}`
    )
    .join(", ");
};

// 'Clara owes Cassidy $21, Ximena owes Cassidy $15'
console.log(whoOwes(receipts));