public class AddTwoNumbers {

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

int carry = 0;

ListNode head = new ListNode(0);

ListNode currNode = head;

while(l1 != null || l2 != null){

int sum = (l1 == null ? 0 : l1.val) + (l2 == null ? 0 : l2.val) + carry;

int val = sum % 10;

carry = sum / 10;

ListNode node = new ListNode(val);

currNode.next = node;

currNode = currNode.next;

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

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

}

if(carry != 0){

ListNode node = new ListNode(carry);

currNode.next = node;

}

return head.next;

}

public static void main(String[] args) {

AddTwoNumbers add = new AddTwoNumbers();

ListNode l1 = new ListNode(7);

ListNode l2 = new ListNode(9);

ListNode l3 = new ListNode(4);

l2.next = l3;

ListNode res = add.addTwoNumbers(l1, l2);

while(res != null){

System.out.print(res.val + " ");

res = res.next;

}

}

}