递归函数来计算总和? [英] Recursive function to calculate sum?

问题描述

这就是我所拥有的，但我不确定为什么它不起作用

This is what I've got and I'm not sure why it's not working

def sum(n):
    if (n>0):
        print (n)
        return sum(n)+sum(n-1)
    else:
        print("done doodly")

number = int(input(":  "))
sum(number)

例如如果使用输入5，我想编程计算5+4+3+2+1的总和.我做错了什么?

For example if the use inputs 5, I want to program to calculate the sum of 5+4+3+2+1. What am I doing wrong ?

推荐答案

两件事:

• 在为 n 计算 sum 时调用 sum(n) 不会对你有多大好处，因为你会无限递归.所以行 return sum(n)+sum(n-1) 是不正确的；它需要是 n 加上 n - 1 其他值的总和.这也很有意义，因为这就是您想要计算的内容.
• 您需要为基本情况和递归情况返回一个值.

• Calling sum(n) when computing sum for n won't do you much good because you'll recurse indefinitely. So the line return sum(n)+sum(n-1) is incorrect; it needs to be n plus the sum of the n - 1 other values. This also makes sense as that's what you want to compute.
• You need to return a value for the base case and for the recursive case.

因此，您可以将代码简化为:

As such you can simplify your code to:

def sum(n):
    if n == 0:
        return 0
    return n + sum(n - 1)

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