Leetcode 2两数相加

思路

按照链表的顺序去取出val 进行相加如果链表长度不同则后补0
相加后进行进位判断

代码

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    
        //不够长后补0
        ListNode res=new ListNode(0);
        ListNode res_next=res;
        int carry=0;
        while(l1!=null||l2!=null){
    
            int a=l1==null?0:l1.val;
            int b=l2==null?0:l2.val;

            int r=a+b+carry;
            carry=r/10;
            r=r%10;
            res_next.next=new ListNode(r);
            res_next=res_next.next;
            if(l1!=null)
                l1=l1.next;
            if(l2!=null)
                l2=l2.next;
            
        }
        if(carry==1)
            res_next.next=new ListNode(carry);
        return res.next;
    }
}