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package com.yangchd.leetcode.medium;

/**

* @author yangchd 2018/3/21.

*

* 2. Add Two Numbers

* 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.

*

* Example:

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

* Output: 7 -> 0 -> 8

* Explanation: 342 + 465 = 807.

*/

public class AddTwoNumbers {

/**

* Definition for singly-linked list.

* public class ListNode {

* int val;

* ListNode next;

* ListNode(int x) { val = x; }

* }

*/

class ListNode {

int val;

ListNode next;

ListNode(int x) {

val = x;

}

}

/**

* 主要就是一位一位加，然后进位。

* 我这里采用的是递归的方法，网上还有一种，是单独设置一个进位标志的方法。

* 运行效率，这个方法也能跑到50ms多点，算比较快的了，所以不改了。

*/

class Solution {

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

ListNode thisNode = new ListNode(l1.val + l2.val);

if(null != l1.next && null != l2.next){

thisNode.next = addTwoNumbers(l1.next,l2.next);

}else if(null == l1.next){

thisNode.next = l2.next;

}else {

thisNode.next = l1.next;

}

checkNumbers(thisNode);

return thisNode;

}

private void checkNumbers(ListNode node){

int num = 10;

while(null != node && node.val >= num){

node.val -= num;

if(null != node.next){

node.next.val += 1;

checkNumbers(node.next);

}else {

node.next = new ListNode(1);

}

}

}

}

}