You are given two non-empty linked lists representing two non-negative integers. The most significant digit comes first and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Follow up:
What if you cannot modify the input lists? In other words, reversing the lists is not allowed.
Example:
Input: (7 -> 2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 8 -> 0 -> 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | # Definition for singly-linked list.# class ListNode:# def __init__(self, x):# self.val = x# self.next = Noneclass Solution: def addTwoNumbers(self, l1, l2): """ :type l1: ListNode :type l2: ListNode :rtype: ListNode """ def list2arr(root): res = [] while root: res.append(root.val) root = root.next return res arr1, arr2 = list2arr(l1), list2arr(l2) index1, index2 = len(arr1) - 1, len(arr2) - 1 carry = 0 root = None while index1 >= 0 or index2 >= 0 or carry: v1, v2 = 0, 0 if index1 >= 0: v1 = arr1[index1] index1 -= 1 if index2 >= 0: v2 = arr2[index2] index2 -= 1 val = (v1 + v2 + carry) carry = 1 if val >= 10 else 0 newNode = ListNode(val % 10) newNode.next = root root = newNode return root |
