leetcode之Add Two Numbers-优快云博客

本文链接：https://blog.youkuaiyun.com/howtogetout/article/details/50019759

本文介绍了一种解决两数相加问题的方法，通过链表来存储数值，并逐位进行加法运算，同时考虑了进位的情况。该算法适用于需要进行大数运算的场景。

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这题其实相当于2个数相加，每一位加每一位。注意有进位。写的不好，代码入下：

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

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        l3 = ListNode(0)
        num1 = 0
        global num1
        def addtwolist(c, a, b):
            global num1
           
            if a != None:
                if b != None:
                    c.val = a.val + b.val + num1
                    if c.val >= 10:
                        c.val = c.val % 10
                        num1 = 1
                    else:
                        num1 = 0
                    if a.next != None or b.next != None:
                        if c.next == None:
                            c.next = ListNode(0)
                    else:
                        if num1 == 1:
                            c.next = ListNode(1)
                    addtwolist(c.next, a.next, b.next)
                else:
                    c.val = a.val + num1
                    if c.val >= 10:
                        c.val = c.val % 10
                        num1 = 1
                    else:
                        num1 = 0
                    if a.next != None:
                        if c.next == None:
                            c.next = ListNode(0)
                    else:
                        if num1 == 1:
                            c.next = ListNode(1)
                    addtwolist(c.next, a.next, None)
            else:
                if b != None:
                    c.val = b.val + num1
                    if c.val >= 10:
                        c.val = c.val % 10
                        num1 = 1
                    else:
                        num1 = 0
                    if b.next != None:
                        if c.next == None:
                            c.next = ListNode(0)
                    else:
                        if num1 == 1:
                            c.next = ListNode(1)
                    addtwolist(c.next, None, b.next)
        addtwolist(l3, l1, l2)
        return l3