【leetcode】2. Add Two Numbers

不能只刷简单题了。从头开始刷，也算加大强度吧。

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

测试用例， 1 999是最好的。
这个考进位，不同的是序列。
自己写的这个分成两部分，一部分是l1,l2一起的同时的时候，其次是处理其中一个不存在的时候，其实是可以把不存在当成0来处理，这样就可以了么。

Your runtime beats 23.66% of javascriptsubmissions.

/** * 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 head = new ListNode(-1);    var node = head;    var singleAdd=function(ll,added,node){        if(added === 0){            node.next = ll;        }else{            var val ;            if(ll !== null){                val = ll.val;                 var num= val+added;                var temp_flag = 0;                if(num >= 10){                   temp_flag = 1;                   num -= 10;                }                node.next = new ListNode(num);                node = node.next;                singleAdd(ll.next,temp_flag,node);            }else{                node.next = new ListNode(1);            }        }    };    var c_flag = 0;    while(l1!== null){      if(l2!==null){          var added_num = l1.val+l2.val+c_flag;          c_flag = 0;          if(added_num>=10){              c_flag = 1;              added_num = added_num -10;          }          var temp = new ListNode(added_num);          node.next = temp;          node = node.next;          l1 = l1.next;          l2 = l2.next;      }else{          singleAdd(l1,c_flag,node);          return head.next;      }    }    singleAdd(l2,c_flag,node);    return head.next;};

逻辑清楚了很多，只是没有
Your runtime beats 32.06% of javascriptsubmissions.

/** * 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 head = new ListNode(-1);    var node = head;    var c_flag=0;    while(l1!== null||l2!==null||c_flag>0){      var val1 = l1===null?0:l1.val;      var val2 = l2 === null ?0:l2.val;      var added_num = val1+val2+c_flag;      c_flag = 0;      if(added_num>=10){          c_flag = 1;          added_num = added_num -10;      }      var temp = new ListNode(added_num);      node.next = temp;      node = node.next;      if(l1!==null){          l1 = l1.next;      }      if(l2!==null){        l2 = l2.next;      }    }    return head.next;};