leetcode-----2. 两数相加

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

思路

  使用正常的数学加法思路，对l1和l2分别进行遍历，数字相加并提取进位放入新的链表中。

代码

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode ans = new ListNode(-1);
        ListNode cur = ans;
        int carry = 0;
        while (l1 != null || l2 != null) {
            int n1 = l1 != null ? l1.val : 0;
            int n2 = l2 != null ? l2.val : 0;
            int sum = n1 + n2 + carry;

            carry = sum / 10;
            cur.next = new ListNode(sum % 10);
            cur = cur.next;
            if (l1 != null) l1 = l1.next;
            if (l2 != null) l2 = l2.next;
        }
        if (carry != 0) cur.next = new ListNode(1);
        return ans.next;
    }
}