[LeetCode][JavaScript]Merge Two Sorted Lists

Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

https://leetcode.com/problems/merge-two-sorted-lists/

指针指来指去。

判断条件里错了几次，if(i.val)会把val===0的情况也排除了，要写成if(i.val !== undefined)

 1 /**
 2  * @param {ListNode} l1
 3  * @param {ListNode} l2
 4  * @return {ListNode}
 5  */
 6 var mergeTwoLists = function(l1, l2) {
 7     var i = l1, j = l2;
 8     var res = new ListNode(-1);
 9     curr = res;
10     while(i && j && i.val !== undefined && j.val !== undefined){
11         if(i.val < j.val){
12             curr.next = i;
13             i = i.next;
14         }else{
15             curr.next = j;
16             j = j.next;
17         }
18         curr = curr.next;     
19     }
20     if(i && i.val !== undefined){
21         curr.next = i;
22     }
23     if(j && j.val !== undefined){
24         curr.next = j;
25     }
26     return res.next || [];
27 };