leetcode AddTwoNumbers 题解

来源：互联网发布：删除表数据 truncate 编辑：程序博客网时间：2024/05/21 11:41

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

题意分析：上面例子中实际指的是 342 + 465 = 807 只是把每个数的每一位给拆开了，用逆向的链表表示出来了。

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; }//next未声明，默认是null，如果val不声明，默认是0. * } */public class Solution {/** * 注意有进位的情况,这里的flag就是保存进位的情况 * 这里需要注意的是 *  ListNode pre = new ListNode(0); *ListNode head = pre; *  这里的pre、head都是引用，指向的都是new ListNode(0)这个实例对象 */    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        ListNode pre = new ListNode(0);ListNode head = pre;int flag = 0;while(l1!=null||l2!=null||flag!=0){    if(l1!=null){        flag+=l1.val;        l1=l1.next;    }    if(l2!=null){        flag+=l2.val;        l2=l2.next;    }    ListNode cur = new ListNode(flag%10);    head.next = cur;    flag=flag/10;    head = head.next;}return pre.next;    }}

1 0