问题描述：

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

代码：

 public ListNode mergeTwoLists(ListNode l1, ListNode l2) {  //java
        if(l2 == null)
        	return l1;
        if(l1 == null)
        	return l2;
        
        ListNode tmp1 = l1;
        ListNode tmp2 = l2;
        ListNode head = new ListNode(0);
        ListNode result = head;
        while(tmp1 != null && tmp2 != null){
        	if(tmp1.val > tmp2.val){
        		ListNode node = new ListNode(tmp2.val);
        		result.next = node;
        		result = result.next;
        		tmp2 = tmp2.next;
        	}
        	
        	else{
        		ListNode node = new ListNode(tmp1.val);
        		result.next = node;
        		result = result.next;
        		tmp1 = tmp1.next;
        	}
        }
        
        if(tmp2 == null)
        	result.next = tmp1;
        else result.next = tmp2;
        
        return head.next;
        	
    }
    public ListNode mergeKLists(List<ListNode> lists) {
        if(lists == null ||lists.size() == 0)
          return null;
         if(lists.size()==1) return lists.get(0);
         return mergeTwoLists(mergeKLists(lists.subList(0,lists.size()/2)),mergeKLists(lists.subList(lists.size()/2,lists.size())));
        
   }

[leetcode]23 Merge k Sorted Lists

原文：http://blog.csdn.net/chenlei0630/article/details/42684393