23. Merge k Sorted Lists（js)

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode[]} lists
 * @return {ListNode}
 */
var mergeKLists = function(lists) {
    if(lists.length===0) return null;
    var n=lists.length;
    while(n>1){
        var k=parseInt((n+1)/2);
        for(var i=0;i<parseInt(n/2);i++){
          lists[i]=  mergeTwoLists(lists[i],lists[i+k]);
        }
        n=k;
    }
    return lists[0];
};
var mergeTwoLists=function(list1,list2){
    var head=new ListNode(-1);
    var curr=head;
    while(list1 && list2){
        if(list1.val<list2.val){
            curr.next=list1;
            list1=list1.next;
        }else{
            curr.next=list2;
            list2=list2.next;
        }
        curr=curr.next;
    }
    if(list1) curr.next=list1;
    if(list2) curr.next=list2;
    return head.next;
}