题解 | #5.合并k个已排序的链表#

每两个一组合并有序链表，将结果覆盖原数组，同时更改数组长度，直至数组长度为1

 function merge(h1,h2){
  let empty = {};
  let pre = empty;
  while(h1!=null && h2!=null){
    if(h1.val<h2.val){
      pre.next = h1;
      h1 = h1.next;
    }else{
      pre.next = h2;
      h2 = h2.next;
    }
    pre = pre.next;
  }
  pre.next = h1!=null ? h1 : h2;
  return empty.next;
}
function mergeKLists(lists) {
  while(lists.length > 1){
    let index = 0;
    for(let i=0; i<lists.length; i+=2){
      lists[index++]  = merge(lists[i],lists[i+1] || null);
    }
    lists.length = index;
  }
  return lists[0];
}