- 第一个方法,brute force,把所有elements收集到arraylist,然后sort,然后存到linked list。
public ListNode mergeKLists(ListNode[] lists) { List<Integer> l = new ArrayList<Integer>(); //存到数组 for (ListNode ln : lists) { while (ln != null) { l.add(ln.val); ln = ln.next; } } //数组排序 Collections.sort(l); //存到链表 ListNode head = new ListNode(0); ListNode h = head; for (int i : l) { ListNode t = new ListNode(i); h.next = t; h = h.next; } h.next = null; return head.next; }
随后像merged two SOrted Lists一样,两辆合并。但是也有小技巧,s.h.i.t
public ListNode mergeTwoLists(ListNode l1, ListNode l2) { ListNode h = new ListNode(0); ListNode ans=h; while (l1 != null && l2 != null) { if (l1.val < l2.val) { h.next = l1; h = h.next; l1 = l1.next; } else { h.next = l2; h = h.next; l2 = l2.next; } } if(l1==null){ h.next=l2; } if(l2==null){ h.next=l1; } return ans.next; } public ListNode mergeKLists(ListNode[] lists) { if(lists.length==1){ return lists[0]; } if(lists.length==0){ return null; } ListNode head = mergeTwoLists(lists[0],lists[1]);//返回的总是排好序的第一个节点 for (int i = 2; i < lists.length; i++) { head = mergeTwoLists(head,lists[i]);//然后和后一个开始交♂换 } return head; }