Question

我编写了这段代码，以添加两个数字存储为Leetcode上的问题的链接列表。我得到的输出表明我的变量没有在while循环中更新，但是我不明白为什么。我想念什么？

# Definition for singly-linked list.
#class ListNode:
#    def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        carrybit = 0
        output = ListNode(0)
        iteration = 0
        while l1.next != None or l2.next != None:
            temp = ListNode((l1.val + l2.val + carrybit)%10)
            if l1.val + l2.val + carrybit > 9:
                carrybit = 1
            else:
                carrybit = 0

            temp2 = output.next
            while temp2 != None:
                temp2 = temp2.next
            temp2 = temp


            l1 = l1.next
            l2 = l2.next

        return output

Answer 1

您正在为本地target_include_directories( ${ELF} PRIVATE "source" "source/target/arm/stm32f1/CMSIS/Device/ST/STM32F1xx/Include" "${tools}\\bin\\../lib/gcc/arm-none-eabi/7.3.1/../../../../arm-none-eabi/include/c++/7.3.1" "${tools}\\bin\\../lib/gcc/arm-none-eabi/7.3.1/../../../../arm-none-eabi/include/c++/7.3.1/arm-none-eabi" "${tools}\\bin\\../lib/gcc/arm-none-eabi/7.3.1/../../../../arm-none-eabi/include/c++/7.3.1/backward" "${tools}\\bin\\../lib/gcc/arm-none-eabi/7.3.1/include" "${tools}\\bin\\../lib/gcc/arm-none-eabi/7.3.1/include-fixed" "${tools}\\bin\\../lib/gcc/arm-none-eabi/7.3.1/../../../../arm-none-eabi/include" )变量分配值。这样做只会更改temp2，temp2或先前的output.next不会被修改。

要更改它，您实际上需要分配给temp2.next。

Answer 2

此代码绝对无效：

        temp2 = output.next
        while temp2 != None:
            temp2 = temp2.next
        temp2 = temp

更新temp2的值，直到达到None，然后将其替换为temp。之后，将不再使用temp2，也不会使用temp。都使用不依赖于此操作结果的新值来重新分配它们。

由于temp被分配了一个新的ListNode，而该ListNode没有链接到任何东西并且从未更改，因此carrybit将超出范围并消失。

发生的唯一另一件事是分配了ListNode，该分配仅在将被丢弃的def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode: output = None lastNode = None carry = 0 while not (l1 is None and l2 is None): if l1 : carry,l1 = l1.val+carry,l1.next if l2 : carry,l2 = l2.val+carry,l2.next nextNode = ListNode(carry%10) carry = carry // 10 if output: lastNode.next = nextNode else : output = nextNode lastNode = nextNode if carry: lastNode.next = ListNode(carry%10) return output中使用。

整个while循环最终什么都不做。

我建议使用一种不太复杂的方法：

» docker build --label $(echo -n 'key="name value"') .
"docker build" requires exactly 1 argument.
See 'docker build --help'.

Usage:  docker build [OPTIONS] PATH | URL | -

Build an image from a Dockerfile

为什么我的链表输出变量在每次循环迭代时都不会更新？

2 个答案: