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.

time: o(max(m,n))

space: o(m+n)

<span style="font-size:14px;">/**
 * 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 head=new ListNode(0);
        ListNode result=head;
        while(l1!=null||l2!=null){
            if(l1!=null){
                carry+=l1.val;
                l1=l1.next;
            }
            
            if(l2!=null){
                carry+=l2.val;
                l2=l2.next;
            }
            
            head.next=new ListNode(carry%10);
            head=head.next;
            carry/=10;
        }
        if(carry==1){
            head.next=new ListNode(1);
        }
       
        return result.next;
    }
}</span>