javascript - 如何使循环购买最大金额？

Question

我正在尝试让我的代码购买最大数量的手机和配件。一部手机售价 99.99，配件售价 9.99。我的银行帐户上有 1000。我如何让我的代码购买最大数量？我的代码目前购买了 9 部手机和 9 部配件。它应该购买 9 部手机和 10 部配件，而不是 9 部。

const ACCESSORY = 9.99;
const PHONE = 99.99;

var balance = 1000;
var total = 0;

var phones_total = 0;
var accessories_total = 0;

while (((total + PHONE) || (total + ACCESSORY)) < balance) {
  total = total + PHONE;
  phones_total = phones_total + 1;
    if ((total + ACCESSORY) < balance) {
      total = total + ACCESSORY;
      accessories_total = accessories_total + 1;
    }
}

console.log("total = " + total);
console.log("phones = " + phones_total);
console.log("accessories = " + accessories_total);

Answer 1

这一行是错误的:

while (((total + PHONE) || (total + ACCESSORY)) < balance) {

这不会测试任何一个总和是否小于 balance . (total + PHONE) || (total + ACCESSORY) 的值总是 total + PHONE除非那是 0 , 然后是 total + ACCESSORY .自 total + PHONE永远不会 0 ，这实际上等同于:

while ((total + PHONE) < balance) {

而且它从不测试是否只有一个配件有可用余额。做这个测试的正确方法是:

while ((total + PHONE) < balance || (total + ACCESSORY) < balance) {

您还应该使用 <=而不是 < , 以便准确使用您所有的钱。

但是在循环中，你仍然添加 PHONE至 total ，即使只剩下足够的余额来购买配件。您需要先检查一下。

const ACCESSORY = 9.99;
const PHONE = 99.99;

var balance = 1000;
var total = 0;

var phones_total = 0;
var accessories_total = 0;

while ((total + PHONE) <= balance || (total + ACCESSORY) <= balance) {
   if ((total + PHONE) <= balance) {
     total = total + PHONE;
     phones_total = phones_total + 1;
   }
   if ((total + ACCESSORY) <= balance) {
     total = total + ACCESSORY;
     accessories_total = accessories_total + 1;
   }
 }

console.log(phones_total, accessories_total);

一个更简单的方法是使用算术而不是循环。将余额除以手机 + 配件的成本，找出您可以负担得起的对数。然后找出您可以用剩下的东西购买多少配件。

const ACCESSORY = 9.99;
const PHONE = 99.99;

var balance = 1000;

var phones_total = Math.floor(balance/(PHONE + ACCESSORY));
var remainder = balance - phones_total*(PHONE+ACCESSORY)
var accessories_total = phones_total + Math.floor(remainder/ACCESSORY);

console.log(phones_total, accessories_total);