2. Add Two Numbers

MediumLinked ListMathSimulationTimeO(max(m, n))SpaceO(max(m, n))

→

carry: 0

2 + 5 + 0 = ?

answer

∅

digit 0: carry in = 0loop

Frame 1 / 13

1class Solution:
2    def addTwoNumbers(self, l1, l2):
3        head = current = None
4        carry = 0
5        while l1 or l2 or carry:
6            val1 = l1.val if l1 else 0
7            val2 = l2.val if l2 else 0
8            total = val1 + val2 + carry
9            carry = total // 10
10            digit = total % 10
11            node = ListNode(digit)
12            if head is None:
13                head = current = node
14            else:
15                current.next = node
16                current = current.next
17            l1 = l1.next if l1 else None
18            l2 = l2.next if l2 else None
19        return head