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

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        dummy = ListNode(0)
        current, carry = dummy, 0

        while l1 or l2:
            val = carry
            if l1:
                val+=l1.val
                l1 = l1.next
            if l2:
                val+=l2.val
                l2 = l2.next
            val, carry = val%10, val/10
            current.next = ListNode(val)
            current = current.next
        if carry == 1:
            current.next = ListNode(carry)
        return dummy.next

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int carry = 0;
        ListNode p, dummy = new ListNode(0);
        p = dummy;
        while(l1 != null || l2 != null || carry != 0) {
            if(l1 != null) {
                carry += l1.val;
                l1 = l1.next;
            }

            if(l2 != null) {
                carry += l2.val;
                l2 = l2.next;
            }

            p.next = new ListNode(carry % 10);
            carry /= 10;
            p = p.next;
        }

        return dummy.next;
    }
}