python - 对分搜索最低付款 (Python) - 答案太大

Question

进行二分搜索以确定一年内还清信用卡余额的最低每月还款额。我的结果总是大了几百，并且无法在MITx:6.00.1x在线提交模块中打印(总是打印0.00)。有人可以提供一些建议吗？

代码:

balance = 999999
annualInterestRate = 0.18
interest = annualInterestRate / 12.0
lower = balance / 12.0
upper = (balance * (1+ interest)**12) / 12.0
guess = (upper + lower) / 2

remainder = balance
newBalance = 0

epsilon = 0.00000001

while (newBalance > epsilon):
    guess = (upper + lower) / 2
    for i in range (0,12):
        newBalance = remainder - guess
        remainder -= guess
        month_interest = newBalance * interest
        remainder = newBalance + month_interest

        if newBalance < 0:
            upper = guess
            newBalance = balance
        elif newBalance > epsilon:
            lower = guess
            newBalance = balance 
print "Lowest Payment: %.2f" %guess 

Answer 1

问题是，您设置了newBalance = 0。因此 while 条件 newBalance > epsilon 永远不会为真，您会直接跳到 print 语句。将 newBalance 设置为 1 或其他值。