Add Two Numbers leetcode java

题目:

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) + (4 -> 6 -> 4)
Output: 6 -> 0 -> 8

 

题解：

这道题就是给的加数是倒着给的，你返回的结果也是倒着写的，所以进位也反着进就好。

维护一个carry，加数大于9时候carry为1，也要注意两个数相加如果大于8的话，要写取模后的值。

 

代码如下：

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        if(l1==null)            return l2;        if(l2==null)            return l1;                int carry = 0;        ListNode newhead = new ListNode(-1);        ListNode l3 = newhead;                while(l1!=null || l2!=null){            if(l1!=null){                carry += l1.val;                l1 = l1.next;            }            if(l2!=null){                carry += l2.val;                l2 = l2.next;            }                        l3.next = new ListNode(carry%10);            carry = carry/10;            l3 = l3.next;        }                if(carry == 1)            l3.next=new ListNode(1);        return newhead.next;    }