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.
/**
* 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 ptr = null;
ListNode output = null;
int carry = 0;
while (l1 != null || l2 != null) {
int val1 = l1 != null? l1.val: 0;
int val2 = l2 != null? l2.val: 0;
int sum = carry + val1 + val2;
carry = sum / 10;
if (output == null) {
output = new ListNode(sum % 10);
ptr = output;
} else {
ptr.next = new ListNode(sum % 10);
ptr = ptr.next;
}
if (l1 != null) l1=l1.next;
if (l2 != null) l2=l2.next;
}
if (carry != 0) {
ptr.next = new ListNode(carry);
}
return output;
}
}
