递增 while 循环在某些测试用例中不起作用

Question

我必须定义一个函数，其中：

Starting with a positive integer original, keep multiplying original by n and calculate the sum of all multiples generated including original until the sum is no longer smaller than total. Return the minimum number of multiplications needed to reach at value at or above the given total.

例如：

multiply_until_total_reached (1,5,2)

1*2=2, (1+2)<5, 2*2=4, (1+2+4)>5, 需要2次乘法
multiply_until_total_reached (1,15,2)

1*2=2, (1+2)<15, 2*2=4, (1+2+4)<15, 4*2=8, (1+2+4+8) =15, 3次乘法

我当前的代码可以正常工作，但在某些情况下返回值相差 1。在 1,1038,2 的情况下，我需要 9 次乘法而不是 10 次，但在 1,15,2 的情况下，我得到正确的 (3) 次乘法。

这是我的代码：

def multiply_until_total_reached(original, total, n):
    if total < original:
        return 0
    elif total > original:
        sumofdigits = 0 #declares var to keep track of sum of digits to compare to total
        timesofmult = 0 #track how many multiplication operations
        while sumofdigits <= total + 1:
            multnum = original * n
            sumofdigits = multnum + original
            original = multnum
            sumofdigits = sumofdigits + multnum
            timesofmult = timesofmult + 1
        return timesofmult

是什么导致它关闭？

Answer 1

试试这个，更小更整洁。解释在评论里..

def multiply_until_total_reached(original, total, n):
        sum = original    #Initialize sum to original
        mult_no = 0

        while sum < total:       #Will auto return 0 if original>=total
            sum += original*n    #Add original * n
            original = original*n   #Update the new original
            mult_no += 1    #Increase multiplications by 1

        return mult_no

print multiply_until_total_reached(1,5,2)
print multiply_until_total_reached(1,15,2)
print multiply_until_total_reached(1,1038,2)

#Output
#2
#3
#10

Answer 2

您的问题是您在每次循环迭代中都重新分配 sumofdigits。您只需在每次迭代 (sumofdigits += multnum) 中将 multnum 添加到 sumofdigits。此外，您的循环条件需要固定为 sumofdigits < total 因为您必须 "Return the minimum number of multiplications needed to reach at value or above the given total."

Answer 3

由于您的代码的解决方案已经发布，并且您接受替代解决方案，请允许我提出以下建议，这充分利用了 Python 的 > 3.2 accumulate() 功能：

from itertools import accumulate, count

def multiply_until_total_reached(original, total, n):
    for i, result in enumerate(accumulate(original*n**c for c in count())):
        if result >= total: return i

assert multiply_until_total_reached(1,5,2) == 2
assert multiply_until_total_reached(1,15,2) == 3
assert multiply_until_total_reached(1,1038,2) == 10

递增 while 循环在某些测试用例中不起作用

Incrementing while loop isn't working in some test cases

python

math

while-loop

python-3.x

calculation