Question

我正在尝试解决此MIT OCW assignment上的第三个问题。它要求您使用二分搜索方法计算在一年内清除给定债务所需的每月付款。我得到了预期的输出类型但结果非常不准确。有人能指出我哪里错了吗？谢谢

# Problem Set 1("C")
# Time Spent: xx hours

def payInOne_BisectionSearch (balance,annualRate):
    #initialize variables
    initialBalance = balance
    monthlyRate = float(annualRate/12.0)
    minMonthly = float(balance/12.0)
    maxMonthly = float((balance * (1 + monthlyRate ** 12.0 ))/12.0)
    monthlyPayment = float((minMonthly + maxMonthly)/2)
    numMonths = 1
    #define function to check balance after 12 months       
    def balanceAfterYear (balance, monthlyRate, monthlyPayment):
        for numMonths in range (1,13):
            interest = balance * monthlyRate
            balance += interest - monthlyPayment
            if balance <= 0:
                  break
        return [balance, numMonths]

    while maxMonthly - minMonthly >= .005:
        balance = initialBalance
        monthlyPayment = float((minMonthly + maxMonthly)/2)
        if balanceAfterYear(balance,monthlyRate,monthlyPayment)[0] < 0:#paying too much
            maxMonthly = monthlyPayment
        elif balanceAfterYear(balance,monthlyRate,monthlyPayment)[0] > 0:#paying too little
            minMonthly = monthlyPayment
        else:
            break
    print "Monthly payment to pay off debt in 1 year:", round(monthlyPayment,2)
    print "Number of months needed:", round(balanceAfterYear(balance,monthlyRate,monthlyPayment)[1], 2) 
    print "Balance:", round(balanceAfterYear(balance,monthlyRate,monthlyPayment)[0], 2) 

payInOne_BisectionSearch (float(raw_input("Enter the outstanding balance")),float(raw_input("Enter annual rate as a decimal")))


    '''Test Case Expected:
       Enter the outstanding balance on your credit card: 320000
       Enter the annual credit card interest rate as a decimal: .2
       RESULT
       Monthly payment to pay off debt in 1 year: 29643.05
       Number of months needed: 12
       Balance: -0.1

       Test Case Actual Output:
       Enter the outstanding balance320000
       Enter annual rate as a decimal.2
       Monthly payment to pay off debt in 1 year: 26666.67
       Number of months needed: 12.0
       Balance: 39179.43'''

Answer 1

您的问题在于您的初始maxMonthly值。我认为你真正喜欢的是它被定义为

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    <img src="<?= Yii::$app->request->baseUrl ?>/img/logo2.png" style="width: 100%;">   
</div>

否则maxMonthly = float((balance * ((1 + monthlyRate) ** 12.0 ))/12.0)将评估为接近零的数字（对于介于0和1之间的monthlyRate**12），这将使maxMonthly评估为monthlyRate与{{1}相同这将使得最后的while循环甚至不会开始。

Python二分搜索逻辑错误 - 返回不准确的结果

1 个答案: