【Leetcode】2. Add Two Numbers

Problem：

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

Resolution

public ListNode addTwoNumbers(ListNode l1,ListNode l2){
    int carry =0;//每一位的数值
    ListNode p,result = new ListNode(0);
    p=result;
    while(l1!=null||l2!=null||carry!=0){
        if(l1!=null){
            carry+=l1.val;
            l1=l1.next;
        }
        if (l2!=null){
           carry+=l2.val;
           l2=l2.next;
        }
        p.next=new ListNode(carry%10);
        carry/10;
        p=p.next;
    }
    return result.next;
}

注：

①需要保证l1或l2非空。在carry！=0时也要继续进行计算的原因是当l1与l2均进行完加法，到达链表末尾，不会出现溢出问题。

②处理方式并非相对l1与l2的val加和在赋值给carry，而是carry+=l1.val，在carry+=l2.val；