2. 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

/**
 * 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) {
        ListNode pl1 = l1;
        ListNode pl2 = l2;
        ListNode head = new ListNode(0);
        ListNode p = head;
        int carry = 0;
        int sum;
        while(pl1!=null && pl2!=null){
            sum = pl1.val + pl2.val + carry; 
            carry = sum>=10?1:0;
            p.next = new ListNode(sum%10);
            p = p.next;
            pl1 = pl1.next;
            pl2 = pl2.next;
        }
        while(pl1!=null){
            sum = pl1.val + carry; 
            carry = sum>=10?1:0;
            p.next = new ListNode(sum%10);
            p = p.next;
            pl1 = pl1.next;
        }
        while(pl2!=null){
            sum = pl2.val + carry; 
            carry = sum>=10?1:0;
            p.next = new ListNode(sum%10);
            p = p.next;
            pl2 = pl2.next;
        }
        if(carry==1){
            p.next = new ListNode(carry);
        }
        return head.next;
    }
}