1. 题目描述

链接：https://leetcode.cn/problems/add-two-numbers/

2. 解题代码

public ListNode AddTwoNumber(ListNode l1, ListNode l2)
{
    ListNode head = new ListNode();
    ListNode cur = head;
    int carry = 0;
    while (l1 != null || l2 != null)
    {
        int val1 = l1 == null ? 0 : l1.val; 
        int val2 = l2 == null ? 0 : l2.val; 

        // 求出商和余数
        int sum = val1 + val2 + carry;
        carry = sum / 10;
        sum %= 10;
        cur.next = new ListNode(sum);

        // 更新链表指向
        cur = cur.next;
        if (l1 != null) l1 = l1.next;
        if (l2 != null) l2 = l2.next;
    }
    if (carry == 1) cur.next = new ListNode(1);
    return head.next;
}