【leetcode】2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

題解如下：

/**
 * 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 dummyHead = new ListNode(0);
        ListNode p = l1;
        ListNode q = l2;
        ListNode cur = dummyHead;
        int carry = 0;
        while(p != null || q != null) {
            int x = (p == null)? 0:p.val;
            int y = (q == null)? 0:q.val;
            int sum = carry + x + y;
            carry = sum / 10;
            cur.next = new ListNode(sum % 10);
            cur = cur.next;
            if(p != null)
                p = p.next;
            if(q != null)
                q = q.next;
        }
        if(carry > 0) {
            cur.next = new ListNode(carry);
        }
        return dummyHead.next;
    }
}