Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Solution:
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ public class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { ListNode rval = null; ListNode current = null; int carry = 0; while(l1 != null || l2 != null) { int subtotal = 0; if(l1 != null && l2 != null) { subtotal = l1.val + l2.val + carry; l1 = l1.next; l2 = l2.next; } // only l2 has content else if (l1 == null) { subtotal = l2.val + carry; l2 = l2.next; } // only l1 has content else { subtotal = l1.val + carry; l1 = l1.next; } if(subtotal > 9) { carry = 1; } else { carry = 0; } ListNode subtotalNode = new ListNode(subtotal % 10); // initialize if(rval == null) { current = subtotalNode; rval = current; } else { current.next = subtotalNode; current = current.next; } } if(carry > 0) { current.next = new ListNode(1); } return rval; } }