Add two numbers represented by linked lists (each node contains a digit) ListNode AddTwoNumbers(ListNode l1, ListNode l2) { ListNode dummy = new ListNode(0); ListNode curr = dummy; int carry = 0; while (l1 != null || l2 != null || carry != 0) { int x = (l1 != null) ?

l1.val : 0;

int y = (l2 != null) ? l2.val : 0;

int sum = x + y + carry;

carry = sum / 10;

curr.next = new ListNode(sum % 10);

curr = curr.next;

if (l1 != null) l1 = l1.next;

if (l2 != null) l2 = l2.next;

Follow on:

return dummy.next;

Explanation:

Add digit by digit with carry, creating new nodes for the result.