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2. Add Two Numbers

2. Add Two Numbers

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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

 


 
 题意一开始还真没看懂,模拟了下,才知道是加法。
直接模拟竖位运算加法,刚好这里也是反着的,加法每次就从最低位开始。如果链表长度不齐,到null了,就赋值0,。最后一位如果进位,别忘记特殊处理,再加一个链表。
 
public class Solution {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        int carry = 0;        ListNode tail = new ListNode(0);        ListNode ptr = tail;        while(l1!=null || l2!=null) {            int tmp1 = 0;//必须要有,避免长度不一样            if(l1!=null) {                tmp1 = l1.val;                l1 = l1.next;            }            int tmp2 = 0;//同上            if(l2!=null) {                tmp2 = l2.val;                l2 = l2.next;            }            int tmp = tmp1 + tmp2 + carry;            carry = tmp/10;            ptr.next = new ListNode(tmp%10);            ptr = ptr.next;        }        //如果两个链表都为空了,但最后一位进了1的情况        if(carry==1) {            ptr.next = new ListNode(1);        }        return tail.next;    }}

 

 

2. Add Two Numbers