2. 两数相加(Medium)

Python示例

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        dummpyHead = ListNode(None)
        p = dummpyHead
        digit = 0
        while l1 or l2: # 两个链表都走完了
            s = 0
            if l1:
                s += l1.val 
                l1 = l1.next 
            if l2:
                s += l2.val 
                l2 = l2.next 
            s += digit
            p.next = ListNode(s % 10)
            p = p.next
            digit = s // 10 
            
        if digit:
            p.next = ListNode(digit)
        return dummpyHead.next