[Algo] 223. 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.  

Example

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

Output: 7 -> 0 -> 8

 

/**
 * class ListNode {
 *   public int value;
 *   public ListNode next;
 *   public ListNode(int value) {
 *     this.value = value;
 *     next = null;
 *   }
 * }
 */
public class Solution {
  public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    // Write your solution here
    ListNode dummy = new ListNode(0);
    ListNode cur = dummy;
    int sum = 0;
    while (l1 != null || l2 != null) {
      if (l1 != null) {
        sum += l1.value;
        l1 = l1.next;
      }
      if (l2 != null) {
        sum += l2.value;
        l2 = l2.next;
      }
      cur.next = new ListNode(sum % 10);
      cur = cur.next;
      sum = sum / 10;
    }
    if (sum == 1) {
      cur.next = new ListNode(1);
    }
    return dummy.next;
  }
}