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HomeWork for [freecodecamp.org]

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function checkCashRegister(price, cash, cid) {
    //计算要找多少钱
    var change = cash - price;
    //从大到小找零
    var newCid = [...cid]
    newCid.reverse()
    //单位面值大小，最大100，从大到小排列备用
    var unitArr = [0.01, 0.05, 0.1, 0.25, 1, 5, 10, 20, 100].reverse()
    //计算可用的金额cidTotal
    var newCidValue = [];
    for (let i = 0; i < newCid.length; i++) {
        newCidValue.push(newCid[i][1])
    }
    var cidTotal = newCidValue.reduce((a, b) => a + b)

    //如果要找的钱与可用金额相等
    if (change === cidTotal) {
        return { status: "CLOSED", change: cid }
    }
    //如果要找的钱大于可用金额
    if (change > cidTotal) {
        return { status: "INSUFFICIENT_FUNDS", change: [] }
    }
    //如果要找的钱小于可用金额  
    if (change < cidTotal) {
        //计算每种面值的货币可用数量newCidNum
        let newCidNum = []
        for (let i = 0; i < newCid.length; i++) {
            newCidNum.push(newCid[i][1] / unitArr[i])
        }

        let final = []
        //从面值最大开始找钱
        for (let i = 0; i < newCid.length; i++) {
            let n = parseInt(change / unitArr[i])
            //面值大的够用，接下来拿面值小的
            if (n <= newCidNum[i]) {
                final.push([newCid[i][0], n * unitArr[i]])
                change = change - n * unitArr[i]
                change = change.toFixed(2)
            }
            //面值大的不够用或者刚好够用，先把面值大的拿完，再拿面值小的
            else {
                final.push(newCid[i])
                change = change - newCid[i][1]
                change = change.toFixed(2)
            }
        }

        //把不需要拿的币值清除
        let newFinal = []
        //统计拿出的钱
        let newTotal = []
        for (let i = 0; i < final.length; i++) {
            if (final[i][1] !== 0) {
                newFinal.push(final[i])
                newTotal.push(final[i][1])
            }
        }

        //如果拿出的钱与要找的钱相等...
        //注意这里为了简化使用的是==，因为reduce()返回的是String
        if (newTotal.reduce((a, b) => a + b).toFixed(2) == cash - price) {
            return { status: "OPEN", change: newFinal };
        }
        //如果拿出来钱与要找的钱不相等...
        //这种情况是因为"找不开"
        else {
            return { status: "INSUFFICIENT_FUNDS", change: [] }
        }
    }


}


console.log(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]]));