leetcode—js—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

解题思路：
（1）本题涉及到链表的结构
（2）本题类似小学数学的加法，从个位开始相加，有超过10则进位，否则就是本节点的值
（3）两个链表的长度不知道谁长，需要做一下处理。

code：

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function(l1, l2) {
    var list = new ListNode(0);
    var result = list;
    var sum, carry = 0;
    while(l1 || l2 || carry>0){  //当l1 或 l2 或有进位存在的时候，加法计算就没有结束
        sum=0;
        if(l1!==null){
            sum += l1.val;
            l1=l1.next;
        }
        if(l2!==null){
            sum += l2.val;
            l2=l2.next;
        }
        sum += carry;
        list.next = new ListNode(sum%10);
        carry = parseInt(sum/10);
        list = list.next;
    }
    return result.next;

};