leetcode-链表-2

/**
 * <p>给你两个 <strong>非空</strong> 的链表，表示两个非负的整数。它们每位数字都是按照 <strong>逆序</strong> 的方式存储的，并且每个节点只能存储 <strong>一位</strong> 数字。</p>
 *
 * <p>请你将两个数相加，并以相同形式返回一个表示和的链表。</p>
 *
 * <p>你可以假设除了数字 0 之外，这两个数都不会以 0 开头。</p>
 *
 * <p> </p>
 *
 * <p><strong>示例 1：</strong></p>
 * <img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2021/01/02/addtwonumber1.jpg" style="width: 483px; height: 342px;" />
 * <pre>
 * <strong>输入：</strong>l1 = [2,4,3], l2 = [5,6,4]
 * <strong>输出：</strong>[7,0,8]
 * <strong>解释：</strong>342 + 465 = 807.
 * </pre>
 *
 * <p><strong>示例 2：</strong></p>
 *
 * <pre>
 * <strong>输入：</strong>l1 = [0], l2 = [0]
 * <strong>输出：</strong>[0]
 * </pre>
 *
 * <p><strong>示例 3：</strong></p>
 *
 * <pre>
 * <strong>输入：</strong>l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
 * <strong>输出：</strong>[8,9,9,9,0,0,0,1]
 * </pre>
 *
 * <p> </p>
 *
 * <p><strong>提示：</strong></p>
 *
 * <ul>
 * <li>每个链表中的节点数在范围 <code>[1, 100]</code> 内</li>
 * <li><code>0 <= Node.val <= 9</code></li>
 * <li>题目数据保证列表表示的数字不含前导零</li>
 * </ul>
 * <div><div>Related Topics</div><div><li>递归</li><li>链表</li><li>数学</li></div></div><br><div><li>👍 8562</li><li>👎 0</li></div>
 */

//leetcode submit region begin(Prohibit modification and deletion)

/**
 * 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 res = new ListNode(0);
        ListNode dummy = res;

        int carry = 0;

        while (l1 != null || l2 != null) {

            int x = l1 == null ? 0 : l1.val;
            int y = l2 == null ? 0 : l2.val;

            //在计算值的时候加上进位
            int sum = x + y + carry;
            carry = sum / 10;
            sum = sum % 10;

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

            if (l1 != null) {
                l1 = l1.next;
            }
            if (l2 != null) {
                l2 = l2.next;
            }

        }
        if (carry == 1) {
            dummy.next = new ListNode(carry);
        }
        return res.next;
    }
}
//leetcode submit region end(Prohibit modification and deletion)