📃 题目描述

题目链接：2. 两数相加 (opens new window)

🔔 解题思路

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(0);
        ListNode cur = dummy;

        int carry = 0;
        while (l1 != null || l2 != null) {
            int sum = (l1 == null ? 0 : l1.val) + (l2 == null ? 0 : l2.val) + carry;
            if (sum >= 10) {
                sum -= 10;
                carry = 1;
            }
            else {
                carry = 0;
            }

            cur.next = new ListNode(sum);
            cur = cur.next;

            l1 = l1 == null ? null : l1.next;
            l2 = l2 == null ? null : l2.next;
        }

        if (carry == 1) {
            cur.next = new ListNode(1);
        }

        return dummy.next;
    }
}

💥 复杂度分析

• 空间复杂度：
• 时间复杂度：