Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

Solution:

  1. /**
  2.  * Definition for singly-linked list.
  3.  * public class ListNode {
  4.  *     int val;
  5.  *     ListNode next;
  6.  *     ListNode(int x) { val = x; }
  7.  * }
  8.  */
  9. public class Solution {
  10.   public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
  11.     ListNode f = new ListNode(0);
  12.     ListNode p = f;
  14.     int c = 0;
  16.     while (l1 != null || l2 != null || c != 0) {
  17.       int a = (l1 == null) ? 0 : l1.val;
  18.       int b = (l2 == null) ? 0 : l2.val;
  19.       int s = a + b + c;
  21.       p.next = new ListNode(s % 10);
  22.       p = p.next;
  24.       if (l1 != null) l1 = l1.next;
  25.       if (l2 != null) l2 = l2.next;
  27.       c = s / 10;
  28.     }
  30.     return f.next;
  31.   }
  32. }