https://www.freecodecamp.cn/challenges/exact-change
设计一个收银程序 checkCashRegister() ，其把购买价格(price)作为第一个参数 , 付款金额 (cash)作为第二个参数, 和收银机中零钱 (cid) 作为第三个参数.
cid 是一个二维数组，存着当前可用的找零.
当收银机中的钱不够找零时返回字符串 "Insufficient Funds". 如果正好则返回字符串 "Closed".
否则, 返回应找回的零钱列表,且由大到小存在二维数组中.
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思路：
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we’ll just think in cents instead of dollars
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Let’s use a simple switch statement and return the value for each type of coin in cents
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Then, while the cash left is greater that the current coin/bill and we still have coins/bills of this type, we remove it’s value from the change left and remove a coin. We’ll keep track of how many coins of each type we’ve given back so we can create an array with the result. Let’s see the code and comment each line:
function checkCashRegister(price, cash, cid) {
cash = cash * 100;
price = price * 100;
var change = cash - price,
changeLeft = change;
var totalCid = getTotalCid(cid);
var result =[];
if (change > totalCid) {
return 'Insufficient Funds';
} else if (change === totalCid) {
return 'Closed';
}
for (var i = cid.length - 1; i >= 0; i--) { // We loop over the cash-in-drawer array in reverse order.
var coinName = cid[i][0], // We set the coin name.
coinTotal = cid[i][1] * 100, // We set the total cash in that type of coin (times 100 for cents!).
coinValue = getValue(coinName), // We get the value of a single coin/bill using it's name.
coinAmount = coinTotal / coinValue, // We get the amount of coins of it's type by dividing the total cash by the value of a single unit.
toReturn = 0; // Counter: How many coins of this type we are returning.
while (changeLeft >= coinValue && coinAmount > 0) { // While change is greater that the value the current coin/bill:
changeLeft -= coinValue; // Substract the value of a single coin/bill from the change left.
coinAmount--; // Remove one coin/bill since we are returning it.
toReturn++; // Add one to the counter.
}
// When the loop is done (because there is no coins/bills of the current
// type left or the change left is less than the value of the current coin/bill)
if (toReturn > 0) {
// We push the coin and total to return in that type of coin/bill to the result.
// We get this value by multiplying the value of a single coin/bill by it's value, and then divide by 100 to get the value in dollars.
result.push([coinName, toReturn * coinValue / 100]);
}
}
// Return something!
// We make use of the getTotalCid method that we created earlier to see how much money we are actually returning.
// If it's not equal to the original change, it means that we can't return that exact amount with the current cash-in-register.
if (getTotalCid(result) !== change) {
return 'Insufficient Funds'; // Return early.
}
return result; // Everything went OK, we return the result!
function getTotalCid(cid) {
var total = 0;
for (var i = 0; i < cid.length; i++) {
total += cid[i][1] * 100;
}
return total;
}
function getValue(coinOrBill) {
switch (coinOrBill) {
case 'PENNY':
return 1;
case 'NICKEL':
return 5;
case 'DIME':
return 10;
case 'QUARTER':
return 25;
case 'ONE':
return 100;
case 'FIVE':
return 500;
case 'TEN':
return 1000;
case 'TWENTY':
return 2000;
case 'ONE HUNDRED':
return 10000;
}
}
}
// Example cash-in-drawer array:
// [["PENNY", 1.01],
// ["NICKEL", 2.05],
// ["DIME", 3.10],
// ["QUARTER", 4.25],
// ["ONE", 90.00],
// ["FIVE", 55.00],
// ["TEN", 20.00],
// ["TWENTY", 60.00],
// ["ONE HUNDRED", 100.00]]
checkCashRegister(18.50, 20.00, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.10], ["QUARTER", 4.25], ["ONE", 90.00], ["FIVE", 55.00], ["TEN", 20.00], ["TWENTY", 60.00], ["ONE HUNDRED", 100.00]]);
