FCC JavaScript Algorithms and Data Structures Projects ( 5 ) :Cash Register

Design a cash register drawer function checkCashRegister() that accepts purchase price as the first argument (price), payment as the second argument (cash), and cash-in-drawer (cid) as the third argument.

cid is a 2D array listing available currency.

The checkCashRegister() function should always return an object with a status key and a change key.

Return {status: "INSUFFICIENT_FUNDS", change: []} if cash-in-drawer is less than the change due, or if you cannot return the exact change.

Return {status: "CLOSED", change: [...]} with cash-in-drawer as the value for the key change if it is equal to the change due.

Otherwise, return {status: "OPEN", change: [...]}, with the change due in coins and bills, sorted in highest to lowest order, as the value of the change key.

Currency Unit	Amount
Penny	$0.01 (PENNY)
Nickel	$0.05 (NICKEL)
Dime	$0.1 (DIME)
Quarter	$0.25 (QUARTER)
Dollar	$1 (ONE)
Five Dollars	$5 (FIVE)
Ten Dollars	$10 (TEN)
Twenty Dollars	$20 (TWENTY)
One-hundred Dollars	$100 (ONE HUNDRED)

Test Case:

checkCashRegister(19.5, 20, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]) should return an object.

checkCashRegister(19.5, 20, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]) should return {status: "OPEN", change: [["QUARTER", 0.5]]}.

checkCashRegister(3.26, 100, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]) should return {status: "OPEN", change: [["TWENTY", 60], ["TEN", 20], ["FIVE", 15], ["ONE", 1], ["QUARTER", 0.5], ["DIME", 0.2], ["PENNY", 0.04]]}.

checkCashRegister(19.5, 20, [["PENNY", 0.01], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]) should return {status: "INSUFFICIENT_FUNDS", change: []}.

checkCashRegister(19.5, 20, [["PENNY", 0.01], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 1], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]) should return {status: "INSUFFICIENT_FUNDS", change: []}.

checkCashRegister(19.5, 20, [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]) should return {status: "CLOSED", change: [["PENNY", 0.5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["FIVE", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]}.

解决方案：

function checkCashRegister(price, cash, cid) {
    //需要返回的对象
    var output = { status: null, change: [] };
    //钱币面值，单位为美分
    var denom = [
        ["ONE HUNDRED", 10000],
        ["TWENTY", 2000],
        ["TEN", 1000],
        ["FIVE", 500],
        ["ONE", 100],
        ["QUARTER", 25],
        ["DIME", 10],
        ["NICKEL", 5],
        ["PENNY", 1]
    ];
    //收银箱中的总额
    var register = cid.reduce((acc, curr) => {
        acc[curr[0]] = Math.round(curr[1] * 100);
        acc.total += acc[curr[0]];
        return acc;
    }, { total: 0 });
    //找零，单位美分
    var change = Math.round((cash - price) * 100);
    // 当找零刚好等于钱柜中的总额
    if (change == register.total) {
        output.status = 'CLOSED';
        output.change = cid;
        return output;
    }
    //当找零大于钱柜中的总额显示金额不足
    if (change > register.total) {
        output.status = 'INSUFFICIENT_FUNDS';
        return output;
    }
    //一般情况，收银箱中的总额大于找零，但不一定就能找零，如果全是大面额的，就无法找零，只能返回金额不足
    var arr = [];
    for (let item of denom) {
        var value = 0;
        while (register[item[0]] > 0 && change >= item[1]) {
            change -= item[1];
            register[item[0]] -= item[1];
            value += item[1];
        }
        if (value > 0) {
            arr.push([item[0], value / 100]);
        }
    }
    //虽然柜子里面的总额超过找零，但是没有小额钱币了，所以显示金额不足
    if (change > 0) {
        output.status = 'INSUFFICIENT_FUNDS';
        return output;
    }
    output.status = 'OPEN';
    output.change = arr;
    return output;
}