[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)

/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
    var i = l1, j = l2;
    var res = new ListNode(-1);
    curr = res;
    while(i && j && i.val !== undefined && j.val !== undefined){
        if(i.val < j.val){
            curr.next = i;
            i = i.next;
        }else{
            curr.next = j;
            j = j.next;
        }
        curr = curr.next;     
    }
    if(i && i.val !== undefined){
        curr.next = i;
    }
    if(j && j.val !== undefined){
        curr.next = j;
    }
    return res.next || [];
};