leetcode445

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode AddTwoNumbers(ListNode l1, ListNode l2) {
        Stack<ListNode> Q1 = new Stack<ListNode>();
            Stack<ListNode> Q2 = new Stack<ListNode>();

            while (l1 != null)
            {
                Q1.Push(l1);
                l1 = l1.next;
            }

            while (l2 != null)
            {
                Q2.Push(l2);
                l2 = l2.next;
            }

            var list = new List<ListNode>();

            var step = ;
            while (Q1.Count >  || Q2.Count > )
            {
                var node1 = new ListNode();
                if (Q1.Count > )
                {
                    node1 = Q1.Pop();
                }

                var node2 = new ListNode();
                if (Q2.Count > )
                {
                    node2 = Q2.Pop();
                }

                var x = node1.val + node2.val + step;
                if (x > )
                {
                    step = ;
                }
                else
                {
                    step = ;
                }

                var node = new ListNode(x % );
                list.Add(node);
            }
            if (step == )
            {
                list.Add(new ListNode());
            }

            list.Reverse();
            var head = list[];
            var temp = head;
            for (int i = ; i < list.Count; i++)
            {
                temp.next = list[i];
                temp = list[i];
            }

            return head;
    }
}

https://leetcode.com/problems/add-two-numbers-ii/#/description

补充一个python的实现：

 class Solution:
     def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
         stack1 = self.buildStack(l1)
         stack2 = self.buildStack(l2)
         head = ListNode(-)
         carry =
         while len(stack1) >  or len(stack2) >  or carry != :
             x =  if len(stack1) ==  else stack1.pop(-)
             y =  if len(stack2) ==  else stack2.pop(-)
             temp = x + y + carry
             carry =  if temp <=  else
             temp = temp %
             node = ListNode(temp)
             node.next = head.next
             head.next = node
         return head.next

     def buildStack(self,node):
         stack = []
         while node != None:
             stack.append(node.val)
             node = node.next
         return stack