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.

Solution

/**
 * 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 t1 = l1, t2 = l2, r = new ListNode(0);
        ListNode now = r;
        boolean f = false;
        while(t1 != null || t2 != null){
            int sum = 0;
            sum += (t1 != null) ? t1.val : 0;
            sum += (t2 != null) ? t2.val : 0;
            if(f == true){
                sum += 1;
                f = false;
            }
            if(sum / 10 != 0){f = true;}
            ListNode node = new ListNode(sum % 10);
            now.next = node;
            now = node;
            if(t1 != null){t1 = t1.next;}
            if(t2 != null){t2 = t2.next;}
        }
        if(f == true){
            ListNode node = new ListNode(1);
            now.next = node;
        }
        return r.next;
    }
}