前端算法-leecode-21 合并了两个有序链表

var mergeTwoLists = function(list1, list2) {
let cur = new ListNode();
let dummy = cur;
while(list1 !== null && list2 !== null){
    if(list1.val<list2.val){
        cur.next = list1;
        list1 = list1.next;
    }else{
        cur.next = list2;
        list2=list2.next;
    }
    cur = cur.next;
}
if(list1 !==null){
    cur.next = list1
}
if(list2 !== null){
    cur.next = list2
}
return dummy.next;
};