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 = 0;
            while (Q1.Count > 0 || Q2.Count > 0)
            {
                var node1 = new ListNode(0);
                if (Q1.Count > 0)
                {
                    node1 = Q1.Pop();
                }

                var node2 = new ListNode(0);
                if (Q2.Count > 0)
                {
                    node2 = Q2.Pop();
                }

                var x = node1.val + node2.val + step;
                if (x > 9)
                {
                    step = 1;
                }
                else
                {
                    step = 0;
                }

                var node = new ListNode(x % 10);
                list.Add(node);
            }
            if (step == 1)
            {
                list.Add(new ListNode(1));
            }

            list.Reverse();
            var head = list[0];
            var temp = head;
            for (int i = 1; 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(-1)
        carry = 0
        while len(stack1) > 0 or len(stack2) > 0 or carry != 0:
            x = 0 if len(stack1) == 0 else stack1.pop(-1)
            y = 0 if len(stack2) == 0 else stack2.pop(-1)
            temp = x + y + carry
            carry = 0 if temp <= 9 else 1
            temp = temp % 10
            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