Question

我需要计算从n到0可以获得的道路数量，但我的代码似乎适用于某些情况而某些情况则不适用。

编辑：当我尝试执行：道路（7,2,3）它显示：

第95行是最后的递归部分

Traceback (most recent call last):
  File "python", line 102, in <module>
  File "python", line 95, in roads
  File "python", line 95, in roads
  File "python", line 95, in roads
TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

def jumps(n, j):

    if n == 0:
        return True
    elif n<0:
        return False
    else:
        if n<j:
            return False
        elif n==j:
            return True
        elif n>j:
            if n%j ==0:
                return True
            else:
                return False

def roads(n, short_jump, long_jump, memo=None):

    if memo == None:
        memo = {}

    if n not in memo:
        if n==0:
            memo[n] = 1
            return memo[n]
        elif n<0:
            memo[n] = 0
            return memo[n]
        else:
            sum_hmrm = 0

            a = jumps(n, short_jump)
            b = jumps(n, long_jump)
            c = n-long_jump
            d = n-short_jump

            if a == True:
                sum_hmrm += 1
            if b == True:
                sum_hmrm += 1

            sum_hmrm += (roads(c, short_jump, long_jump, memo) + roads(d, short_jump, long_jump, memo))

            memo[n] = sum_hmrm
            return memo[n]

Answer 1

问题与你如何进行记忆有关。代码的主体以if n not in memo为条件。但是，如果不满足该条件，则根本不执行任何操作。这意味着如果您尝试重新计算已经评估的值，则返回None而不是缓存的值。

我认为您要删除缩进的return行，并在函数末尾添加一行不在if语句中：

if n not in memo:
    if n==0:
        memo[n] = 1 # remove return after this line
    elif n<0:
        memo[n] = 0 # and here
    else:
        sum_hmrm = 0

        a = jumps(n, short_jump)
        b = jumps(n, long_jump)
        c = n-long_jump
        d = n-short_jump

        if a == True:
            sum_hmrm += 1
        if b == True:
            sum_hmrm += 1

        sum_hmrm += (roads(c, short_jump, long_jump, memo) + roads(d, short_jump, long_jump, memo))

        memo[n] = sum_hmrm # the one after this line can just be unindented

return memo[n]

Python中的道路计算（递归）

1 个答案: