使用链表仅对偶数求和? [英] Using linked lists to sum only even numbers?

问题描述

我一直在尝试在 python 中使用链表来根据列表中的偶数计算列表的总和.我已经为我相信的链表部分编写了代码，但我很难理解如何让它实际只取偶数并将它们相加.我的代码现在看起来像这样:

I've been trying to use linked lists in python to calculate the sum of a list based on the even numbers within that list. I've written the code for the linked list portion I believe but I'm stumped on how to get it to actually take the even numbers only and sum them. My code right now looks something like this:

def createList(plist):
    linkedList = None
    # goes backwards, adding each element to the beginning
    # of the list.  
    for index in range(len(plist)-1, -1, -1):
        linkedList = insertValueHead(linkedList, plist[index])
    return linkedList

def sumEvens(linkedList): #This is what I'm looking for help with
    ....


def testSumEvens():
    myList = createList([14, 21, 29, 2, 16, 49, -26])
    print "The sum of the even numbers in the first list is ", sumEvens(myList)
    myList = createList([])
    print "The sum of the even numbers in an empty list is ", sumEvens(myList)
    myList = createList([5, 15, 25])
    print "The sume of the even numbers in the final list is ", sumEvens(myList)

我将如何着手创建这些列表的总和?比如第一个，14+2+16?

How would I go about making this create a sum of these lists? Such as in the first, 14 + 2 + 16?

推荐答案

@filmor 是对的..

@filmor is right..

这是您需要的吗?

def createList(*args):
    new_list=[]

    for arg in args: 
        new_list.append(arg)

    return new_list

def sumEvens(List):

    if List:
        return sum(x for x in List if x % 2 == 0)
    else:
        return "0"


def testSumEvens():
    myList = createList(14, 21, 29, 2, 16, 49, -26)

    print "The sum of the even numbers in the first list is {0}".format(sumEvens(myList))
    myList = createList()
    print "The sum of the even numbers in an empty list is {0}".format(sumEvens(myList))
    myList = createList(5, 15, 25)
    print "The sum of the even numbers in the final list is {0}".format(sumEvens(myList))

testSumEvens()

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