Amount of combinations with nominals given

Question

I am to calculate the amount of combinations of a number (let's call it C) using N numbers given. I am to use a recursive formula. However there is an error:
"TypeError: unsupported operand type(s) for +=: 'int' and 'NoneType' "
My code:

def amount(N, C, latest_nominal = 0):
    if C < 0:
        return print("C should be positive")
    if C == 0:
        return print("1")
    if not N:
        return print("There are no nominals")
    possibilities = 0
    for nominal in N:
        if nominal >= latest_nominal:
            possibilities += amount(N, C-nominal, nominal)
    return possibilities

I would appreciate any help! :)

Kevin Wang Kevin Wang · Accepted Answer · 2017-01-11T21:05:21

the print() function returns None.

So when you do return print("C should be positive"), you are returning None. Hence, at the line possibilities += amount(N, C-nominal, nominal) your code is raising Exception

Amount of combinations with nominals given

1 Answers