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>